linkedin.php

<?php

/**
 * This file defines the 'LinkedIn' class. This class is designed to be a 
 * simple, stand-alone implementation of the most-used LinkedIn API functions.
 * 
 * COPYRIGHT:
 *   
 * Copyright (C) 2011, fiftyMission Inc.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a 
 * copy of this software and associated documentation files (the "Software"), 
 * to deal in the Software without restriction, including without limitation 
 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in 
 * all copies or substantial portions of the Software.  
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 
 * IN THE SOFTWARE.  
 *
 * SOURCE CODE LOCATION:
 * 
 * http://code.google.com/p/simple-linkedinphp/
 *    
 * REQUIREMENTS:
 * 
 * 1. You must have cURL installed on the server and available to PHP.
 * 2. You must be running PHP 5+.  
 *  
 * QUICK START:
 * 
 * There are two files needed to enable LinkedIn API functionality from PHP; the
 * stand-alone OAuth library, and this LinkedIn class. The latest version of 
 * the stand-alone OAuth library can be found on Google Code:
 * 
 * http://code.google.com/p/oauth/
 *   
 * Install these two files on your server in a location that is accessible to 
 * the scripts you wish to use them in. Make sure to change the file 
 * permissions such that your web server can read the files.
 * 
 * Next, make sure the path to the OAuth library is correct (you can change this 
 * as needed, depending on your file organization scheme, etc).
 * 
 * Finally, test the class by attempting to connect to LinkedIn using the 
 * associated demo.php page, also located at the Google Code location
 * referenced above.                   
 *   
 * RESOURCES:
 *    
 * LinkedIn API Documentation from developer.linkedin.com
 * Access Out-Of-Network Profiles:  http://developer.linkedin.com/docs/DOC-1160 
 * Comments Network Updates:	      http://developer.linkedin.com/docs/DOC-1043 
 * Company Search API:              http://developer.linkedin.com/docs/DOC-1325 
 * Connections API:				          http://developer.linkedin.com/docs/DOC-1004
 * Experience Levels:               http://developer.linkedin.com/docs/DOC-1155  
 * Field Selectors:				          http://developer.linkedin.com/docs/DOC-1014 
 * Get Network Updates:			        http://developer.linkedin.com/docs/DOC-1006 
 * Industry Codes:				          http://developer.linkedin.com/docs/DOC-1011 
 * Invitation API:				          http://developer.linkedin.com/docs/DOC-1012 
 * Job Bookmarks and Suggestions:   http://developer.linkedin.com/docs/DOC-1323 
 * Job Functions:                   http://developer.linkedin.com/docs/DOC-1143 
 * Job Lookup API:                  http://developer.linkedin.com/docs/DOC-1322
 * Job Posting API:                 http://developer.linkedin.com/docs/DOC-1142
 * Job Search API:                  http://developer.linkedin.com/docs/DOC-1321
 * Job Types:                       http://developer.linkedin.com/docs/DOC-1144  
 * JSON Requests & Responses:       http://developer.linkedin.com/docs/DOC-1203 
 * Messaging API:					          http://developer.linkedin.com/docs/DOC-1044 
 * People Search API:					      http://developer.linkedin.com/docs/DOC-1191
 *   replaces Search API:           http://developer.linkedin.com/docs/DOC-1005
 * Profile API:					            http://developer.linkedin.com/docs/DOC-1002
 * Profile Fields:				          http://developer.linkedin.com/docs/DOC-1061
 * Post Network Update:		          http://developer.linkedin.com/docs/DOC-1009
 * Share API:                       http://developer.linkedin.com/docs/DOC-1212 
 *   replaces Status Update API:	  http://developer.linkedin.com/docs/DOC-1007
 * Throttle Limits:                 http://developer.linkedin.com/docs/DOC-1112
 *                                  http://developer.linkedin.com/message/4626#4626
 *                                  http://developer.linkedin.com/message/3193#3193 
 *    
 * @version 3.1.1 - July 12, 2011
 * @author Paul Mennega <paul@fiftymission.net>
 * @copyright Copyright 2011, fiftyMission Inc. 
 * @license http://www.opensource.org/licenses/mit-license.php The MIT License 
 */
 
/**
 * Source: http://code.google.com/p/oauth/
 * 
 * Rename and move as needed, changing the require_once() call to the correct 
 * name and path.
 */    
if(!extension_loaded('oauth')) {
  // the PECL OAuth extension is not present, load our third-party OAuth library
  require_once('OAuth.php');
} else {
  // the PECL extension is present, which is not compatible with this library
  throw new LinkedInException('Simple-LinkedIn: library not compatible with installed PECL OAuth extension.  Please disable this extension to use the Simple-LinkedIn library.');
}

/**
 * 'LinkedInException' class declaration.
 *  
 * This class extends the base 'Exception' class.
 * 
 * @access public
 * @package classpackage
 */
class LinkedInException extends Exception {}

/**
 * 'LinkedIn' class declaration.
 *  
 * This class provides generalized LinkedIn oauth functionality.
 * 
 * @access public
 * @package classpackage
 */
class LinkedIn {
  // api/oauth settings
  const _API_OAUTH_REALM             = 'http://api.linkedin.com';
  const _API_OAUTH_VERSION           = '1.0';
  
  // the default response format from LinkedIn
  const _DEFAULT_RESPONSE_FORMAT     = 'xml';
    
  // helper constants used to standardize LinkedIn <-> API communication.  See demo page for usage.
  const _GET_RESPONSE                = 'lResponse';
  const _GET_TYPE                    = 'lType';
  
  // Invitation API constants.
  const _INV_SUBJECT                 = 'Invitation to connect';
  const _INV_BODY_LENGTH             = 200;
  
  // API methods
  const _METHOD_TOKENS               = 'POST';
  
  // Network API constants.
  const _NETWORK_LENGTH              = 1000;
  const _NETWORK_HTML                = '<a>';
  
  // response format type constants, see http://developer.linkedin.com/docs/DOC-1203
  const _RESPONSE_JSON               = 'JSON';
  const _RESPONSE_JSONP              = 'JSONP';
  const _RESPONSE_XML                = 'XML';
  
  // Share API constants
  const _SHARE_COMMENT_LENGTH        = 700;
  const _SHARE_CONTENT_TITLE_LENGTH  = 200;
  const _SHARE_CONTENT_DESC_LENGTH   = 400;
  
  // LinkedIn API end-points
	const _URL_ACCESS                  = 'https://api.linkedin.com/uas/oauth/accessToken';
	const _URL_API                     = 'https://api.linkedin.com';
	const _URL_AUTH                    = 'https://www.linkedin.com/uas/oauth/authenticate?oauth_token=';
	const _URL_REQUEST                 = 'https://api.linkedin.com/uas/oauth/requestToken';
	const _URL_REVOKE                  = 'https://api.linkedin.com/uas/oauth/invalidateToken';
	
	// Library version
	const _VERSION                     = '3.1.1';
  
  // oauth properties
  protected $callback;
  protected $token                   = NULL;
  
  // application properties
  protected $application_key, 
            $application_secret;
  
  // the format of the data to return
  protected $response_format         = self::_DEFAULT_RESPONSE_FORMAT;

  // last request fields
  public $last_request_headers, 
         $last_request_url;

	/**
	 * Create a LinkedIn object, used for OAuth-based authentication and 
	 * communication with the LinkedIn API.	 
	 * 
	 * @param arr $config
	 *         The 'start-up' object properties:
	 *           - appKey       => The application's API key
	 *           - appSecret    => The application's secret key
	 *           - callbackUrl  => [OPTIONAL] the callback URL
	 *                 	 
	 * @return obj
	 *         A new LinkedIn object.	 
	 */
	public function __construct($config) {
    if(!is_array($config)) {
      // bad data passed
		  throw new LinkedInException('LinkedIn->__construct(): bad data passed, $config must be of type array.');
    }
    $this->setApplicationKey($config['appKey']);
	  $this->setApplicationSecret($config['appSecret']);
	  $this->setCallbackUrl($config['callbackUrl']);
	}
	
	/**
   * The class destructor.
   * 
   * Explicitly clears LinkedIn object from memory upon destruction.
	 */
  public function __destruct() {
    unset($this);
	}
	
	/**
	 * Bookmark a job.
	 * 
	 * Calling this method causes the current user to add a bookmark for the 
	 * specified job:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1323
	 * 
	 * @param str $jid
	 *         Job ID you want to bookmark.
	 *         	 
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function bookmarkJob($jid) {
	  // check passed data
	  if(!is_string($jid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->bookmarkJob(): bad data passed, $jid must be of type string.');
	  }
	  
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/people/~/job-bookmarks';
	  $response = $this->fetch('POST', $query, '<job-bookmark><job><id>' . trim($jid) . '</id></job></job-bookmark>');
	  
	  /**
	   * Check for successful request (a 201 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
		return $this->checkResponse(201, $response);
	}
	
	/**
	 * Get list of jobs you have bookmarked.
	 * 
	 * Returns a list of jobs the current user has bookmarked, per:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1323   
	 * 	
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function bookmarkedJobs() {	
    // construct and send the request  
	  $query    = self::_URL_API . '/v1/people/~/job-bookmarks';
	  $response = $this->fetch('GET', $query);
	  
	  /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
		return $this->checkResponse(200, $response);
	}
	
	/**
	 * Used to check whether a response LinkedIn object has the required http_code or not and 
	 * returns an appropriate LinkedIn object.
	 * 
	 * @param int $http_code_required
	 * 		     The required http response from LinkedIn.
	 * @param arr $response 
	 *         An array containing a LinkedIn response.
	 * 
	 * @return arr
	 * 	       An array containing a LinkedIn response with appropriate values
	 */
	private function checkResponse($http_code_required, $response) {
		// check passed data
    if(!is_array($response)) {
			throw new LinkedInException('LinkedIn->checkResponse(): $response must be an array');
		}
		if(!is_int($http_code_required)) {
			throw new LinkedInException('LinkedIn->checkResponse(): $http_code_required must be an integer value');
		}
		
		// check the response
		if($response['info']['http_code'] == $http_code_required) {
		  //request successful
		  $response['success'] = TRUE;
		} else {
			//request failed
			$response['success'] = FALSE;
			$response['error']   = 'HTTP response from LinkedIn end-point was not code ' . $http_code_required;
		}
		return $response;
	}
	
	/**
	 * Close a job.
	 * 
	 * Calling this method causes the passed job to be closed, per:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1151   
	 * 
	 * @param str $jid
	 *         Job ID you want to close.
	 *            	
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function closeJob($jid) {
	  // check passed data
	  if(!is_string($jid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->closeJob(): bad data passed, $jid must be of string value.');
	  }
	  
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/jobs/partner-job-id=' . trim($jid);
	  $response = $this->fetch('DELETE', $query);
	  
	  /**
	   * Check for successful job close (a 204 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(204, $response);
	}
	
	/**
	 * Share comment posting method.
	 * 
	 * Post a comment on an existing connections shared content. API details can
	 * be found here: 
	 * 
	 * http://developer.linkedin.com/docs/DOC-1043 
	 * 
	 * @param str $uid 
	 *         The LinkedIn update ID.   	 
	 * @param str $comment 
	 *         The share comment to be posted.
	 *            	 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.       	 
	 */
	public function comment($uid, $comment) {
	  // check passed data
	  if(!is_string($uid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->comment(): bad data passed, $uid must be of type string.');
	  }
    if(!is_string($comment)) {
      // nothing/non-string passed, raise an exception
		  throw new LinkedInException('LinkedIn->comment(): bad data passed, $comment must be a non-zero length string.');
    }
    
    /**
     * Share comment rules:
     * 
     * 1) No HTML permitted.
     * 2) Comment cannot be longer than 700 characters.     
     */
    $comment = substr(trim(htmlspecialchars(strip_tags($comment))), 0, self::_SHARE_COMMENT_LENGTH);
		$data    = '<?xml version="1.0" encoding="UTF-8"?>
                <update-comment>
  				        <comment>' . $comment . '</comment>
  				      </update-comment>';

    // construct and send the request
    $query    = self::_URL_API . '/v1/people/~/network/updates/key=' . $uid . '/update-comments';
    $response = $this->fetch('POST', $query, $data);
    
    /**
	   * Check for successful comment (a 201 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */ 
    return $this->checkResponse(201, $response);
	}
	
	/**
	 * Share comment retrieval.
	 *     
	 * Return all comments associated with a given network update:
	 * 	 
	 *   http://developer.linkedin.com/docs/DOC-1043
	 * 
	 * @param str $uid
	 *         The LinkedIn update ID.
	 *                     	 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.                  
	 */
	public function comments($uid) {
	  // check passed data
	  if(!is_string($uid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->comments(): bad data passed, $uid must be of type string.');
	  }
		
		// construct and send the request
    $query    = self::_URL_API . '/v1/people/~/network/updates/key=' . $uid . '/update-comments';
    $response = $this->fetch('GET', $query);
    
  	/**
	   * Check for successful comments retrieval (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */ 
    return $this->checkResponse(200, $response);
	}
	
	/**
	 * Company profile retrieval function.
	 * 
	 * Takes a string of parameters as input and requests company profile data 
	 * from the LinkedIn Company Profile API. See the official documentation for 
	 * $options 'field selector' formatting:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1014
	 *   http://developer.linkedin.com/docs/DOC-1259   
	 * 
	 * @param str $options
	 *         Data retrieval options.	
	 * @param	bool $by_email
	 *         [OPTIONAL] Search by email domain?
	 * 	 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function company($options, $by_email = FALSE) {
	  // check passed data
	  if(!is_string($options)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->company(): bad data passed, $options must be of type string.');
	  }
	  if(!is_bool($by_email)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->company(): bad data passed, $by_email must be of type boolean.');
	  }
	  
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/companies' . ($by_email ? '' : '/') . trim($options);
	  $response = $this->fetch('GET', $query);
	  
	  /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
	
  /**
	 * Company products and their associated recommendations.
	 * 
	 * The product data type contains details about a company's product or 
	 * service, including recommendations from LinkedIn members, and replies from 
	 * company representatives.
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1327   
	 * 
	 * @param str $cid
	 *         Company ID you want the producte for.	
	 * @param str $options
	 *         [OPTIONAL] Data retrieval options.
	 *            	
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function companyProducts($cid, $options = '') {
	  // check passed data
	  if(!is_string($cid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->companyProducts(): bad data passed, $cid must be of type string.');
	  }
	  if(!is_string($options)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->companyProducts(): bad data passed, $options must be of type string.');
	  }
	  
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/companies/' . trim($cid) . '/products' . trim($options);
	  $response = $this->fetch('GET', $query);
	  
	  /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
  	
	/**
	 * Connection retrieval function.
	 * 
	 * Takes a string of parameters as input and requests connection-related data 
	 * from the Linkedin Connections API. See the official documentation for 
	 * $options 'field selector' formatting:
	 * 
	 * http://developer.linkedin.com/docs/DOC-1014      	 
	 * 
	 * @param str $options 
	 *         [OPTIONAL] Data retrieval options.
	 *            	 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function connections($options = '~/connections') {
	  // check passed data
	  if(!is_string($options)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->connections(): bad data passed, $options must be of type string.');
	  }
	  
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/people/' . trim($options);
	  $response = $this->fetch('GET', $query);
	  
	  /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
	
	/**
	 * Edit a job.
	 * 
	 * Calling this method causes the passed job to be edited, with the passed
	 * XML instructing which fields to change, per:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1154
	 *   http://developer.linkedin.com/docs/DOC-1142      
	 * 
	 * @param str $jid
	 *         Job ID you want to renew.
	 * @param str $xml
	 *         The XML containing the job fields to edit.	 
	 *            	
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function editJob($jid, $xml) {
	  // check passed data
	  if(!is_string($jid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->editJob(): bad data passed, $jid must be of string value.');
	  }
	  if(is_string($xml)) {
	    $xml = trim(stripslashes($xml));
	  } else {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->editJob(): bad data passed, $xml must be of string value.');
	  }
               
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/jobs/partner-job-id=' . trim($jid);
	  $response = $this->fetch('PUT', $query, $xml);
	  
	  /**
	   * Check for successful job renewal (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
	
	/**
	 * General data send/request method.
	 * 
	 * @param str $method 
	 *         The data communication method.	 
	 * @param str $url 
	 *         The Linkedin API endpoint to connect with.
	 * @param str $data
	 *         [OPTIONAL] The data to send to LinkedIn.
	 * @param arr $parameters 
	 *         [OPTIONAL] Addition OAuth parameters to send to LinkedIn.
	 *        
	 * @return arr 
	 *         Array containing:
	 * 
	 *           array(
	 *             'info'      =>	Connection information,
	 *             'linkedin'  => LinkedIn response,  
	 *             'oauth'     => The OAuth request string that was sent to LinkedIn	 
	 *           )	 
	 */
	protected function fetch($method, $url, $data = NULL, $parameters = array()) {
	  // check for cURL
	  if(!extension_loaded('curl')) {
	    // cURL not present
      throw new LinkedInException('LinkedIn->fetch(): PHP cURL extension does not appear to be loaded/present.');
	  }
	  
    try {
	    // generate OAuth values
	    $oauth_consumer  = new OAuthConsumer($this->getApplicationKey(), $this->getApplicationSecret(), $this->getCallbackUrl());
	    $oauth_token     = $this->getToken();
	    $oauth_token     = (!is_null($oauth_token)) ? new OAuthToken($oauth_token['oauth_token'], $oauth_token['oauth_token_secret']) : NULL;
      $defaults        = array(
        'oauth_version' => self::_API_OAUTH_VERSION
      );
	    $parameters    = array_merge($defaults, $parameters);
	    
	    // generate OAuth request
  		$oauth_req = OAuthRequest::from_consumer_and_token($oauth_consumer, $oauth_token, $method, $url, $parameters);
      $oauth_req->sign_request(new OAuthSignatureMethod_HMAC_SHA1(), $oauth_consumer, $oauth_token);
      
      // start cURL, checking for a successful initiation
      if(!$handle = curl_init()) {
         // cURL failed to start
        throw new LinkedInException('LinkedIn->fetch(): cURL did not initialize properly.');
      }
      
      // set cURL options, based on parameters passed
	    curl_setopt($handle, CURLOPT_CUSTOMREQUEST, $method);
      curl_setopt($handle, CURLOPT_RETURNTRANSFER, TRUE);
      curl_setopt($handle, CURLOPT_SSL_VERIFYPEER, FALSE);
      curl_setopt($handle, CURLOPT_URL, $url);
      curl_setopt($handle, CURLOPT_VERBOSE, FALSE);
      
      // configure the header we are sending to LinkedIn - http://developer.linkedin.com/docs/DOC-1203
      $header = array($oauth_req->to_header(self::_API_OAUTH_REALM));
      if(is_null($data)) {
        // not sending data, identify the content type
        $header[] = 'Content-Type: text/plain; charset=UTF-8';
        switch($this->getResponseFormat()) {
          case self::_RESPONSE_JSON:
            $header[] = 'x-li-format: json';
            break;
          case self::_RESPONSE_JSONP:
            $header[] = 'x-li-format: jsonp';
            break;
        }
      } else {
        $header[] = 'Content-Type: text/xml; charset=UTF-8';
        curl_setopt($handle, CURLOPT_POSTFIELDS, $data);
      }
      curl_setopt($handle, CURLOPT_HTTPHEADER, $header);
    
      // set the last url, headers
      $this->last_request_url = $url;
      $this->last_request_headers = $header;
      
      // gather the response
      $return_data['linkedin']        = curl_exec($handle);
      $return_data['info']            = curl_getinfo($handle);
      $return_data['oauth']['header'] = $oauth_req->to_header(self::_API_OAUTH_REALM);
      $return_data['oauth']['string'] = $oauth_req->base_string;
            
      // check for throttling
      if(self::isThrottled($return_data['linkedin'])) {
        throw new LinkedInException('LinkedIn->fetch(): throttling limit for this user/application has been reached for LinkedIn resource - ' . $url);
      }
      
      //TODO - add check for NO response (http_code = 0) from cURL
      
      // close cURL connection
      curl_close($handle);
      
      // no exceptions thrown, return the data
      return $return_data;
    } catch(OAuthException $e) {
      // oauth exception raised
      throw new LinkedInException('OAuth exception caught: ' . $e->getMessage());
    }
	}
	
	/**
	 * Follow a company.
	 * 
	 * Calling this method causes the current user to start following the 
	 * specified company, per:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1324
	 * 
	 * @param str $cid
	 *         Company ID you want to follow.
	 *         	 
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function followCompany($cid) {
	  // check passed data
	  if(!is_string($cid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->followCompany(): bad data passed, $cid must be of type string.');
	  }
	  
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/people/~/following/companies';
	  $response = $this->fetch('POST', $query, '<company><id>' . trim($cid) . '</id></company>');
	  
	  /**
	   * Check for successful request (a 201 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(201, $response);
	}
	
	/**
	 * Get list of companies you follow.
	 * 
	 * Returns a list of companies the current user is currently following, per:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1324   
	 * 	
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function followedCompanies() {	  
	  // construct and send the request
    $query    = self::_URL_API . '/v1/people/~/following/companies';
	  $response = $this->fetch('GET', $query);
	  
	  /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
	
	/**
	 * Get the application_key property.
	 * 
	 * @return str 
	 *         The application key.       	 
	 */
	public function getApplicationKey() {
	  return $this->application_key;
	}
	
	/**
	 * Get the application_secret property.
	 * 
	 * @return str 
	 *         The application secret.       	 
	 */
	public function getApplicationSecret() {
	  return $this->application_secret;
	}
	
	/**
	 * Get the callback property.
	 * 
	 * @return str 
	 *         The callback url.       	 
	 */
	public function getCallbackUrl() {
	  return $this->callback;
	}
  
  /**
	 * Get the response_format property.
	 * 
	 * @return str 
	 *         The response format.       	 
	 */
	public function getResponseFormat() {
	  return $this->response_format;
	}
	
	/**
	 * Get the token_access property.
	 * 
	 * @return arr 
	 *         The access token.       	 
	 */
	public function getToken() {
	  return $this->token;
	}
	
	/**
	 * [DEPRECATED] Get the token_access property.
	 * 
	 * @return arr 
	 *         The access token.       	 
	 */
	public function getTokenAccess() {
	  return $this->getToken();
	}
	
	/**
	 * Send connection invitations.
	 *     
	 * Send an invitation to connect to your network, either by email address or 
	 * by LinkedIn ID. Details on the API here: 
	 * 
	 * http://developer.linkedin.com/docs/DOC-1012
	 * 
	 * @param str $method 
	 *         The invitation method to process.	 
	 * @param str $recipient 
	 *         The email/id to send the invitation to.	 	 
	 * @param str $subject 
	 *         The subject of the invitation to send.
	 * @param str $body 
	 *         The body of the invitation to send.
	 * @param str $type 
	 *         [OPTIONAL] The invitation request type (only friend is supported at this time by the Invite API).
	 * 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.  	 
	 */
	public function invite($method, $recipient, $subject, $body, $type = 'friend') {
    /**
     * Clean up the passed data per these rules:
     * 
     * 1) Message must be sent to one recipient (only a single recipient permitted for the Invitation API)
     * 2) No HTML permitted
     * 3) 200 characters max in the invitation subject
     * 4) Only able to connect as a friend at this point     
     */
    // check passed data
    if(empty($recipient)) {
   		throw new LinkedInException('LinkedIn->invite(): you must provide an invitation recipient.');
    }
    switch($method) {
      case 'email':
        if(is_array($recipient)) {
          $recipient = array_map('trim', $recipient);
        } else {
          // bad format for recipient for email method
          throw new LinkedInException('LinkedIn->invite(): invitation recipient email/name array is malformed.');
        }
        break;
      case 'id':
        $recipient = trim($recipient);
        if(!self::isId($recipient)) {
          // bad format for recipient for id method
          throw new LinkedInException('LinkedIn->invite(): invitation recipient ID does not match LinkedIn format.');
        }
        break;
      default:
        throw new LinkedInException('LinkedIn->invite(): bad invitation method, must be one of: email, id.');
        break;
    }
    if(!empty($subject)) {
      $subject = trim(htmlspecialchars(strip_tags(stripslashes($subject))));
    } else {
      throw new LinkedInException('LinkedIn->invite(): message subject is empty.');
    }
    if(!empty($body)) {
      $body = trim(htmlspecialchars(strip_tags(stripslashes($body))));
      if(strlen($body) > self::_INV_BODY_LENGTH) {
        throw new LinkedInException('LinkedIn->invite(): message body length is too long - max length is ' . self::_INV_BODY_LENGTH . ' characters.');
      }
    } else {
      throw new LinkedInException('LinkedIn->invite(): message body is empty.');
    }
    switch($type) {
      case 'friend':
        break;
      default:
        throw new LinkedInException('LinkedIn->invite(): bad invitation type, must be one of: friend.');
        break;
    }
    
    // construct the xml data
		$data   = '<?xml version="1.0" encoding="UTF-8"?>
		           <mailbox-item>
		             <recipients>
                   <recipient>';
                     switch($method) {
                       case 'email':
                         // email-based invitation
                         $data .= '<person path="/people/email=' . $recipient['email'] . '">
                                     <first-name>' . htmlspecialchars($recipient['first-name']) . '</first-name>
                                     <last-name>' . htmlspecialchars($recipient['last-name']) . '</last-name>
                                   </person>';
                         break;
                       case 'id':
                         // id-based invitation
                         $data .= '<person path="/people/id=' . $recipient . '"/>';
                         break;
                     }
    $data  .= '    </recipient>
                 </recipients>
                 <subject>' . $subject . '</subject>
                 <body>' . $body . '</body>
                 <item-content>
                   <invitation-request>
                     <connect-type>';
                       switch($type) {
                         case 'friend':
                           $data .= 'friend';
                           break;
                       }
    $data  .= '      </connect-type>';
                     switch($method) {
                       case 'id':
                         // id-based invitation, we need to get the authorization information
                         $query                 = 'id=' . $recipient . ':(api-standard-profile-request)';
                         $response              = self::profile($query);
                         if($response['info']['http_code'] == 200) {
                           $response['linkedin'] = self::xmlToArray($response['linkedin']);
                           if($response['linkedin'] === FALSE) {
                             // bad XML data
                             throw new LinkedInException('LinkedIn->invite(): LinkedIn returned bad XML data.');
                           }
                           $authentication = explode(':', $response['linkedin']['person']['children']['api-standard-profile-request']['children']['headers']['children']['http-header']['children']['value']['content']);
                           
                           // complete the xml        
                           $data .= '<authorization>
                                       <name>' . $authentication[0] . '</name>
                                       <value>' . $authentication[1] . '</value>
                                     </authorization>';
                         } else {
                           // bad response from the profile request, not a valid ID?
                           throw new LinkedInException('LinkedIn->invite(): could not send invitation, LinkedIn says: ' . print_r($response['linkedin'], TRUE));
                         }
                         break;
                     }
    $data  .= '    </invitation-request>
                 </item-content>
               </mailbox-item>';
    
    // send request
    $query    = self::_URL_API . '/v1/people/~/mailbox';
    $response = $this->fetch('POST', $query, $data);
		
		/**
	   * Check for successful update (a 201 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */ 
    return $this->checkResponse(201, $response);
	}
	
	/**
	 * LinkedIn ID validation.
	 *	 
	 * Checks the passed string $id to see if it has a valid LinkedIn ID format, 
	 * which is, as of October 15th, 2010:
	 * 
	 *   10 alpha-numeric mixed-case characters, plus underscores and dashes.          	 
	 * 
	 * @param str $id 
	 *         A possible LinkedIn ID.         	 
	 * 
	 * @return bool 
	 *         TRUE/FALSE depending on valid ID format determination.                  
	 */
	public static function isId($id) {
	  // check passed data
    if(!is_string($id)) {
	    // bad data passed
	    throw new LinkedInException('LinkedIn->isId(): bad data passed, $id must be of type string.');
	  }
	  
	  $pattern = '/^[a-z0-9_\-]{10}$/i';
	  if($match = preg_match($pattern, $id)) {
	    // we have a match
	    $return_data = TRUE;
	  } else {
	    // no match
	    $return_data = FALSE;
	  }
	  return $return_data;
	}
	
	/**
	 * Throttling check.
	 * 
	 * Checks the passed LinkedIn response to see if we have hit a throttling 
	 * limit:
	 * 
	 * http://developer.linkedin.com/docs/DOC-1112
	 * 
	 * @param arr $response 
	 *         The LinkedIn response.
	 *                     	 
	 * @return bool
	 *         TRUE/FALSE depending on content of response.                  
	 */
	public static function isThrottled($response) {
	  $return_data = FALSE;
    
    // check the variable
	  if(!empty($response) && is_string($response)) {
	    // we have an array and have a properly formatted LinkedIn response
	       
      // store the response in a temp variable
      $temp_response = self::xmlToArray($response);
  	  if($temp_response !== FALSE) {
    	  // check to see if we have an error
    	  if(array_key_exists('error', $temp_response) && ($temp_response['error']['children']['status']['content'] == 403) && preg_match('/throttle/i', $temp_response['error']['children']['message']['content'])) {
    	    // we have an error, it is 403 and we have hit a throttle limit
  	      $return_data = TRUE;
    	  }
  	  }
  	}
  	return $return_data;
	}
	
	/**
	 * Job posting detail info retrieval function.
	 * 
	 * The Jobs API returns detailed information about job postings on LinkedIn. 
	 * Find the job summary, description, location, and apply our professional graph 
	 * to present the relationship between the current member and the job poster or 
	 * hiring manager.
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1322  
	 * 
	 * @param	str $jid 
	 *         ID of the job you want to look up.
	 * @param str $options 
	 *         [OPTIONAL] Data retrieval options.
	 *            	
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function job($jid, $options = '') {
	  // check passed data
	  if(!is_string($jid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->job(): bad data passed, $jid must be of type string.');
	  }
	  if(!is_string($options)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->job(): bad data passed, $options must be of type string.');
	  }
	  
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/jobs/' . trim($jid) . trim($options);
	  $response = $this->fetch('GET', $query);
	  
	  /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
	
	/**
	 * Returns the last request header from the previous call to the 
	 * LinkedIn API.
	 * 
	 * @returns str
	 *           The header, in string format.
	 */            	
	public function lastRequestHeader() {
	   return $this->last_request_headers;
	}
	
	/**
	 * Returns the last request url from the previous call to the 
	 * LinkedIn API.
	 * 
	 * @returns str
	 *           The url, in string format.
	 */            	
	public function lastRequestUrl() {
	   return $this->last_request_url;
	}
	
	/**
	 * Like another user's network update:
	 * 
	 * http://developer.linkedin.com/docs/DOC-1043
	 * 
	 * @param str $uid
	 *         The LinkedIn update ID.
	 *                     	 
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.                  
	 */
	public function like($uid) {
	  // check passed data
	  if(!is_string($uid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->like(): bad data passed, $uid must be of type string.');
	  }
    
    // construct the xml data
		$data = '<?xml version="1.0" encoding="UTF-8"?>
		         <is-liked>true</is-liked>';
		
		// send request
    $query    = self::_URL_API . '/v1/people/~/network/updates/key=' . $uid . '/is-liked';
    $response = $this->fetch('PUT', $query, $data);
    
  	/**
	   * Check for successful like (a 201 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */ 
    return $this->checkResponse(201, $response);
	}
	
	/**
	 * Retrieve network update likes.
	 *    
	 * Return all likes associated with a given network update:
	 * 
	 * http://developer.linkedin.com/docs/DOC-1043
	 * 
	 * @param str $uid
	 *         The LinkedIn update ID.
	 *                     	 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.                  
	 */
	public function likes($uid) {
	  // check passed data
	  if(!is_string($uid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->likes(): bad data passed, $uid must be of type string.');
	  }
		
		// construct and send the request
    $query    = self::_URL_API . '/v1/people/~/network/updates/key=' . $uid . '/likes';
    $response = $this->fetch('GET', $query);
    
  	/**
	   * Check for successful likes retrieval (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */ 
    return $this->checkResponse(200, $response);
	}
	
	/**
	 * Connection messaging method.
	 * 	 
	 * Send a message to your network connection(s), optionally copying yourself.  
	 * Full details from LinkedIn on this functionality can be found here: 
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1044
	 * 
	 * @param arr $recipients 
	 *         The connection(s) to send the message to.	 	 
	 * @param str $subject 
	 *         The subject of the message to send.
	 * @param str $body 
	 *         The body of the message to send.
	 * @param bool $copy_self 
	 *         [OPTIONAL] Also update the teathered Twitter account.
	 *    	 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.      	 
	 */
	public function message($recipients, $subject, $body, $copy_self = FALSE) {
    /**
     * Clean up the passed data per these rules:
     * 
     * 1) Message must be sent to at least one recipient
     * 2) No HTML permitted
     */
    if(!empty($subject) && is_string($subject)) {
      $subject = trim(strip_tags(stripslashes($subject)));
    } else {
      throw new LinkedInException('LinkedIn->message(): bad data passed, $subject must be of type string.');
    }
    if(!empty($body) && is_string($body)) {
      $body = trim(strip_tags(stripslashes($body)));
    } else {
      throw new LinkedInException('LinkedIn->message(): bad data passed, $body must be of type string.');
    }
    if(!is_array($recipients) || count($recipients) < 1) {
      // no recipients, and/or bad data
      throw new LinkedInException('LinkedIn->message(): at least one message recipient required.');
    }
    
    // construct the xml data
		$data   = '<?xml version="1.0" encoding="UTF-8"?>
		           <mailbox-item>
		             <recipients>';
    $data  .=     ($copy_self) ? '<recipient><person path="/people/~"/></recipient>' : '';
                  for($i = 0; $i < count($recipients); $i++) {
                    if(is_string($recipients[$i])) {
                      $data .= '<recipient><person path="/people/' . trim($recipients[$i]) . '"/></recipient>';
                    } else {
                      throw new LinkedInException ('LinkedIn->message(): bad data passed, $recipients must be an array of type string.');
                    }
                  }
    $data  .= '  </recipients>
                 <subject>' . htmlspecialchars($subject) . '</subject>
                 <body>' . htmlspecialchars($body) . '</body>
               </mailbox-item>';
    
    // send request
    $query    = self::_URL_API . '/v1/people/~/mailbox';
    $response = $this->fetch('POST', $query, $data);
		
		/**
	   * Check for successful update (a 201 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */ 
    return $this->checkResponse(201, $response);
	}
	
	/**
	 * Job posting method.
	 * 	 
	 * Post a job to LinkedIn, assuming that you have access to this feature. 
	 * Full details from LinkedIn on this functionality can be found here: 
	 * 
	 *   http://developer.linkedin.com/community/jobs?view=documents
	 * 
	 * @param str $xml 
	 *         The XML defining a job to post.	 	 
	 *    	 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.      	 
	 */
	public function postJob($xml) {
    // check passed data
    if(is_string($xml)) {
      $xml = trim(stripslashes($xml));
    } else {
      throw new LinkedInException('LinkedIn->postJob(): bad data passed, $xml must be of type string.');
    }
   
    // construct and send the request
    $query    = self::_URL_API . '/v1/jobs';
    $response = $this->fetch('POST', $query, $xml);
		
		/**
	   * Check for successful job post (a 201 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */ 
    return $this->checkResponse(201, $response);
	}
	
	/**
	 * General profile retrieval function.
	 * 
	 * Takes a string of parameters as input and requests profile data from the 
	 * Linkedin Profile API. See the official documentation for $options
	 * 'field selector' formatting:
	 * 
	 * http://developer.linkedin.com/docs/DOC-1014
	 * http://developer.linkedin.com/docs/DOC-1002    
	 * 
	 * @param str $options 
	 *         [OPTIONAL] Data retrieval options.
	 *            	 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function profile($options = '~') {
	  // check passed data
	  if(!is_string($options)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->profile(): bad data passed, $options must be of type string.');
	  }
	  
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/people/' . trim($options);
	  $response = $this->fetch('GET', $query);
	  
	  /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
	
	/**
	 * Renew a job.
	 * 
	 * Calling this method causes the passed job to be renewed, per:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1154   
	 * 
	 * @param str $jid
	 *         Job ID you want to renew.
	 * @param str $cid
	 *         Contract ID that covers the passed Job ID.	 
	 *            	
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function renewJob($jid, $cid) {
	  // check passed data
	  if(!is_string($jid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->renewJob(): bad data passed, $jid must be of string value.');
	  }
	  if(!is_string($cid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->renewJob(): bad data passed, $cid must be of string value.');
	  }
	  
	  // construct the xml data
		$data   = '<?xml version="1.0" encoding="UTF-8"?>
		           <job>
		             <contract-id>' . trim($cid) . '</contract-id>
                 <renewal/>
               </job>';
               
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/jobs/partner-job-id=' . trim($jid);
	  $response = $this->fetch('PUT', $query, $data);
	  
	  /**
	   * Check for successful job renewal (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
	
  /**
	 * Access token retrieval.
	 *
	 * Request the user's access token from the Linkedin API.
	 * 
	 * @param str $token
	 *         The token returned from the user authorization stage.
	 * @param str $secret
	 *         The secret returned from the request token stage.
	 * @param str $verifier
	 *         The verification value from LinkedIn.
	 *    	 
	 * @return arr 
	 *         The Linkedin OAuth/http response, in array format.      	 
	 */
	public function retrieveTokenAccess($token, $secret, $verifier) {
	  // check passed data
    if(!is_string($token) || !is_string($secret) || !is_string($verifier)) {
      // nothing passed, raise an exception
		  throw new LinkedInException('LinkedIn->retrieveTokenAccess(): bad data passed, string type is required for $token, $secret and $verifier.');
    }
    
    // start retrieval process
	  $this->setToken(array('oauth_token' => $token, 'oauth_token_secret' => $secret));
    $parameters = array(
      'oauth_verifier' => $verifier
    );
    $response = $this->fetch(self::_METHOD_TOKENS, self::_URL_ACCESS, NULL, $parameters);
    parse_str($response['linkedin'], $response['linkedin']);
    
    /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
    if($response['info']['http_code'] == 200) {
      // tokens retrieved
      $this->setToken($response['linkedin']);
      
      // set the response
      $return_data            = $response;
      $return_data['success'] = TRUE;
    } else {
      // error getting the request tokens
       $this->setToken(NULL);
       
      // set the response
      $return_data            = $response;
      $return_data['error']   = 'HTTP response from LinkedIn end-point was not code 200';
      $return_data['success'] = FALSE;
    }
    return $return_data;
	}
	
	/**
	 * Request token retrieval.
	 * 
	 * Get the request token from the Linkedin API.
	 * 
	 * @return   arr                   The Linkedin OAuth/http response, in array format.      	 
	 */
	public function retrieveTokenRequest() {
    $parameters = array(
      'oauth_callback' => $this->getCallbackUrl()
    );
    $response = $this->fetch(self::_METHOD_TOKENS, self::_URL_REQUEST, NULL, $parameters);
    parse_str($response['linkedin'], $response['linkedin']);
    
    /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
    if(($response['info']['http_code'] == 200) && (array_key_exists('oauth_callback_confirmed', $response['linkedin'])) && ($response['linkedin']['oauth_callback_confirmed'] == 'true')) {
      // tokens retrieved
      $this->setToken($response['linkedin']);
      
      // set the response
      $return_data            = $response;
      $return_data['success'] = TRUE;        
    } else {
      // error getting the request tokens
      $this->setToken(NULL);
      
      // set the response
      $return_data = $response;
      if((array_key_exists('oauth_callback_confirmed', $response['linkedin'])) && ($response['linkedin']['oauth_callback_confirmed'] == 'true')) {
        $return_data['error'] = 'HTTP response from LinkedIn end-point was not code 200';
      } else {
        $return_data['error'] = 'OAuth callback URL was not confirmed by the LinkedIn end-point';
      }
      $return_data['success'] = FALSE;
    }
    return $return_data;
	}
	
	/**
	 * User authorization revocation.
	 * 
	 * Revoke the current user's access token, clear the access token's from 
	 * current LinkedIn object. The current documentation for this feature is 
	 * found in a blog entry from April 29th, 2010:
	 * 
	 *   http://developer.linkedin.com/community/apis/blog/2010/04/29/oauth--now-for-authentication	 
	 * 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.   	 
	 */
	public function revoke() {
	  // construct and send the request
	  $response = $this->fetch('GET', self::_URL_REVOKE);

	  /**
	   * Check for successful revocation (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */                	  
    return $this->checkResponse(200, $response);
	}
	
	/**
	 * [DEPRECATED] General people search function.
	 * 
	 * Takes a string of parameters as input and requests profile data from the 
	 * Linkedin People Search API.  See the official documentation for $options
	 * querystring formatting:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1191 
	 * 
	 * @param str $options 
	 *         [OPTIONAL] Data retrieval options.
	 *            	 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function search($options = NULL) {
		return searchPeople($options);
	}
	
	/**
	 * Company search.
	 * 
	 * Uses the Company Search API to find companies using keywords, industry, 
	 * location, or some other criteria. It returns a collection of matching 
	 * companies.
	 * 
	 * http://developer.linkedin.com/docs/DOC-1325  
	 * 
	 * @param str $options
	 *         [OPTIONAL] Search options.	
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function searchCompanies($options = '') {
	  // check passed data
	  if(!is_string($options)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->searchCompanies(): bad data passed, $options must be of type string.');
	  }
	  
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/company-search' . trim($options);
	  $response = $this->fetch('GET', $query);
	  
	  /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
	
	/**
	 * Jobs search.
	 * 
	 * Use the Job Search API to find jobs using keywords, company, location, 
	 * or some other criteria. It returns a collection of matching jobs. Each 
	 * entry can contain much of the information available on the job listing.
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1321  
	 * 
	 * @param str $options 
	 *         [OPTIONAL] Data retrieval options.
	 *            	
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function searchJobs($options = '') {
	  // check passed data
	  if(!is_string($options)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->jobsSearch(): bad data passed, $options must be of type string.');
	  }
	  
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/job-search' . trim($options);
	  $response = $this->fetch('GET', $query);
	  
	  /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
	
	/**
	 * General people search function.
	 * 
	 * Takes a string of parameters as input and requests profile data from the 
	 * Linkedin People Search API.  See the official documentation for $options
	 * querystring formatting:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1191 
	 * 
	 * @param str $options 
	 *         [OPTIONAL] Data retrieval options.
	 *            	 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function searchPeople($options = NULL) {
	  // check passed data
    if(!is_null($options) && !is_string($options)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->search(): bad data passed, $options must be of type string.');
	  }
	  
	  // construct and send the request
    $query    = self::_URL_API . '/v1/people-search' . trim($options);
		$response = $this->fetch('GET', $query);
		
		/**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
		return $this->checkResponse(200, $response);
	}
	
	/**
	 * Set the application_key property.
	 * 
	 * @param str $key 
	 *         The application key.       	 
	 */
	public function setApplicationKey($key) {
	  $this->application_key = $key;
	}
	
	/**
	 * Set the application_secret property.
	 * 
	 * @param str $secret 
	 *         The application secret.       	 
	 */
	public function setApplicationSecret($secret) {
	  $this->application_secret = $secret;
	}
	
	/**
	 * Set the callback property.
	 * 
	 * @param str $url 
	 *         The callback url.       	 
	 */
	public function setCallbackUrl($url) {
	  $this->callback = $url;
	}
	
	/**
	 * Set the response_format property.
	 * 
	 * @param str $format 
	 *         [OPTIONAL] The response format to specify to LinkedIn.       	 
	 */
	public function setResponseFormat($format = self::_DEFAULT_RESPONSE_FORMAT) {
	  $this->response_format = $format;
	}
	
	/**
	 * Set the token property.
	 * 
	 * @return arr $token 
	 *         The LinkedIn OAuth token.
	 */
	public function setToken($token) {
    // check passed data
    if(!is_null($token) && !is_array($token)) {
      // bad data passed
      throw new LinkedInException('LinkedIn->setToken(): bad data passed, $token_access should be in array format.');
    }
    
    // set token
    $this->token = $token;
	}
	
	/**
	 * [DEPRECATED] Set the token_access property.
	 * 
	 * @return arr $token_access 
	 *         [OPTIONAL] The LinkedIn OAuth access token.
	 */
	public function setTokenAccess($token_access) {
    $this->setToken($token_access);
	}
	
	/**
	 * Post a share. 
	 * 
	 * Create a new or reshare another user's shared content. Full details from 
	 * LinkedIn on this functionality can be found here: 
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1212 
	 * 
	 *   $action values: ('new', 'reshare')      	 
	 *   $content format: 
	 *     $action = 'new'; $content => ('comment' => 'xxx', 'title' => 'xxx', 'submitted-url' => 'xxx', 'submitted-image-url' => 'xxx', 'description' => 'xxx')
	 *     $action = 'reshare'; $content => ('comment' => 'xxx', 'id' => 'xxx')	 
	 * 
	 * @param str $action
	 *         The sharing action to perform.	 
	 * @param str $content
	 *         The share content.
	 * @param bool $private 
	 *         [OPTIONAL] Should we restrict this shared item to connections only?	 
	 * @param bool $twitter 
	 *         [OPTIONAL] Also update the teathered Twitter account.
	 *    	 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.      	 
	 */
	public function share($action, $content, $private = TRUE, $twitter = FALSE) {
	  // check the status itself
    if(!empty($action) && !empty($content)) {
      /**
       * Status is not empty, wrap a cleaned version of it in xml.  Status
       * rules:
       * 
       * 1) Comments are 700 chars max (if this changes, change _SHARE_COMMENT_LENGTH constant)
       * 2) Content/title 200 chars max (if this changes, change _SHARE_CONTENT_TITLE_LENGTH constant)
       * 3) Content/description 400 chars max (if this changes, change _SHARE_CONTENT_DESC_LENGTH constant)
       * 4a) New shares must contain a comment and/or (content/title and content/submitted-url)
       * 4b) Reshared content must contain an attribution id.
       * 4c) Reshared content must contain actual content, not just a comment.             
       * 5) No HTML permitted in comment, content/title, content/description.
       */

      // prepare the share data per the rules above
      $share_flag   = FALSE;
      $content_xml  = NULL;
      switch($action) {
        case 'new':
          // share can be an article
          if(array_key_exists('title', $content) && array_key_exists('submitted-url', $content)) {
            // we have shared content, format it as needed per rules above
            $content_title = trim(htmlspecialchars(strip_tags(stripslashes($content['title']))));
            if(strlen($content_title) > self::_SHARE_CONTENT_TITLE_LENGTH) {
              throw new LinkedInException('LinkedIn->share(): title length is too long - max length is ' . self::_SHARE_CONTENT_TITLE_LENGTH . ' characters.');
            }
            $content_xml .= '<content>
                               <title>' . $content_title . '</title>
                               <submitted-url>' . trim(htmlspecialchars($content['submitted-url'])) . '</submitted-url>';
            if(array_key_exists('submitted-image-url', $content)) {
              $content_xml .= '<submitted-image-url>' . trim(htmlspecialchars($content['submitted-image-url'])) . '</submitted-image-url>';
            }
            if(array_key_exists('description', $content)) {
              $content_desc = trim(htmlspecialchars(strip_tags(stripslashes($content['description']))));
              if(strlen($content_desc) > self::_SHARE_CONTENT_DESC_LENGTH) {
                throw new LinkedInException('LinkedIn->share(): description length is too long - max length is ' . self::_SHARE_CONTENT_DESC_LENGTH . ' characters.');
              }
              $content_xml .= '<description>' . $content_desc . '</description>';
            }
            $content_xml .= '</content>';
            
            $share_flag = TRUE;
          }
          
          // share can be just a comment
          if(array_key_exists('comment', $content)) {
          	// comment located
          	$comment = htmlspecialchars(trim(strip_tags(stripslashes($content['comment']))));
          	if(strlen($comment) > self::_SHARE_COMMENT_LENGTH) {
              throw new LinkedInException('LinkedIn->share(): comment length is too long - max length is ' . self::_SHARE_COMMENT_LENGTH . ' characters.');
            }
            $content_xml .= '<comment>' . $comment . '</comment>';
          	
          	$share_flag = TRUE; 
      	  }
          break;
        case 'reshare':
          if(array_key_exists('id', $content)) {
            // put together the re-share attribution XML
            $content_xml .= '<attribution>
                               <share>
                                 <id>' . trim($content['id']) . '</id>
                               </share>
                             </attribution>';
            
            // optional additional comment
            if(array_key_exists('comment', $content)) {
            	// comment located
            	$comment = htmlspecialchars(trim(strip_tags(stripslashes($content['comment']))));
            	if(strlen($comment) > self::_SHARE_COMMENT_LENGTH) {
                throw new LinkedInException('LinkedIn->share(): comment length is too long - max length is ' . self::_SHARE_COMMENT_LENGTH . ' characters.');
              }
              $content_xml .= '<comment>' . $comment . '</comment>';
        	  }
        	  
        	  $share_flag = TRUE;
          }
          break;
        default:
          // bad action passed
          throw new LinkedInException('LinkedIn->share(): share action is an invalid value, must be one of: share, reshare.');
          break;
      }
      
      // should we proceed?
      if($share_flag) {
        // put all of the xml together
        $visibility = ($private) ? 'connections-only' : 'anyone';
        $data       = '<?xml version="1.0" encoding="UTF-8"?>
                       <share>
                         ' . $content_xml . '
                         <visibility>
                           <code>' . $visibility . '</code>
                         </visibility>
                       </share>';
        
        // create the proper url
        $share_url = self::_URL_API . '/v1/people/~/shares';
  		  if($twitter) {
  			  // update twitter as well
          $share_url .= '?twitter-post=true';
  			}
        
        // send request
        $response = $this->fetch('POST', $share_url, $data);
  		} else {
  		  // data contraints/rules not met, raise an exception
		    throw new LinkedInException('LinkedIn->share(): sharing data constraints not met; check that you have supplied valid content and combinations of content to share.');
  		}
    } else {
      // data missing, raise an exception
		  throw new LinkedInException('LinkedIn->share(): sharing action or shared content is missing.');
    }
    
    /**
	   * Check for successful update (a 201 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */ 
    return $this->checkResponse(201, $response);
	}
	
	/**
	 * Network statistics.
	 * 
	 * General network statistics retrieval function.
	 * 
	 * Returns the number of connections, second-connections an authenticated
	 * user has.  More information here:
	 * 
	 * http://developer.linkedin.com/docs/DOC-1006
	 * 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function statistics() {
	  // construct and send the request
    $query    = self::_URL_API . '/v1/people/~/network/network-stats';
		$response = $this->fetch('GET', $query);
		
		/**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
		return $this->checkResponse(200, $response);
	}
	
	/**
	 * Companies you may want to follow.
	 * 
	 * Returns a list of companies the current user may want to follow, per:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1324   
	 * 
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function suggestedCompanies() {
	  // construct and send the request
    $query    = self::_URL_API . '/v1/people/~/suggestions/to-follow/companies';
	  $response = $this->fetch('GET', $query);
	  
	  /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
	
	/**
	 * Jobs you may be interested in.
	 * 
	 * Returns a list of jobs the current user may be interested in, per:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1323   
	 * 
 	 * @param str $options
 	 *         [OPTIONAL] Data retrieval options.	
 	 *          	 
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function suggestedJobs($options = ':(jobs)') {
	  // check passed data
	  if(!is_string($options)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->suggestedJobs(): bad data passed, $options must be of type string.');
	  }
	
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/people/~/suggestions/job-suggestions' . trim($options);
	  $response = $this->fetch('GET', $query);
	  
	  /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
	
	/**
	 * Unbookmark a job.
	 * 
	 * Calling this method causes the current user to remove a bookmark for the 
	 * specified job:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1323   
	 * 
	 * @param str $jid
	 *         Job ID you want to unbookmark.
	 *            	
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function unbookmarkJob($jid) {
	  // check passed data
	  if(!is_string($jid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->unbookmarkJob(): bad data passed, $jid must be of type string.');
	  }
	  
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/people/~/job-bookmarks/' . trim($jid);
	  $response = $this->fetch('DELETE', $query);
	  
	  /**
	   * Check for successful request (a 204 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(204, $response);
	}
	
	/**
	 * Unfollow a company.
	 * 
	 * Calling this method causes the current user to stop following the specified 
	 * company, per:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1324   
	 * 
	 * @param str $cid
	 *         Company ID you want to unfollow.	
	 *         	 
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function unfollowCompany($cid) {
	  // check passed data
	  if(!is_string($cid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->unfollowCompany(): bad data passed, $cid must be of string value.');
	  }
	  
	  // construct and send the request
	  $query    = self::_URL_API . '/v1/people/~/following/companies/id=' . trim($cid);
	  $response = $this->fetch('DELETE', $query);
	  
	  /**
	   * Check for successful 'unfollow' (a 204 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(204, $response);
	}
	
	/**
	 * Unlike a network update.
	 *     
	 * Unlike another user's network update:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1043
	 * 
	 * @param str $uid 
	 *         The LinkedIn update ID.
	 *                     	 
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.                  
	 */
	public function unlike($uid) {
	  // check passed data
	  if(!is_string($uid)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->unlike(): bad data passed, $uid must be of type string.');
	  }
    
    // construct the xml data
		$data = '<?xml version="1.0" encoding="UTF-8"?>
		         <is-liked>false</is-liked>';
		
		// send request
    $query    = self::_URL_API . '/v1/people/~/network/updates/key=' . $uid . '/is-liked';
    $response = $this->fetch('PUT', $query, $data);
    
  	/**
	   * Check for successful 'unlike' (a 201 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */ 
    return $this->checkResponse(201, $response);
	}
	
	/**
	 * Post network update.
	 * 
	 * Update the user's Linkedin network status. Full details from LinkedIn 
	 * on this functionality can be found here: 
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1009
	 *   http://developer.linkedin.com/docs/DOC-1009#comment-1077 
	 * 
	 * @param str $update
	 *         The network update.	 
	 * 
	 * @return arr 
	 *         Array containing retrieval success, LinkedIn response.       	 
	 */
	public function updateNetwork($update) {
	  // check passed data
    if(!is_string($update)) {
      // nothing/non-string passed, raise an exception
		  throw new LinkedInException('LinkedIn->updateNetwork(): bad data passed, $update must be a non-zero length string.');
    }
    
    /**
     * Network update is not empty, wrap a cleaned version of it in xml.  
     * Network update rules:
     * 
     * 1) No HTML permitted except those found in _NETWORK_HTML constant
     * 2) Update cannot be longer than 140 characters.     
     */
    // get the user data
    $response = self::profile('~:(first-name,last-name,site-standard-profile-request)');
    if($response['success'] === TRUE) {
      /** 
       * We are converting response to usable data.  I'd use SimpleXML here, but
       * to keep the class self-contained, we will use a portable XML parsing
       * routine, self::xmlToArray.       
       */
      $person = self::xmlToArray($response['linkedin']);
      if($person === FALSE) {
        // bad xml data
        throw new LinkedInException('LinkedIn->updateNetwork(): LinkedIn returned bad XML data.');
      }
  		$fields = $person['person']['children'];
  
  		// prepare user data
  		$first_name   = trim($fields['first-name']['content']);
  		$last_name    = trim($fields['last-name']['content']);
  		$profile_url  = trim($fields['site-standard-profile-request']['children']['url']['content']);
  
      // create the network update 
      $update = trim(htmlspecialchars(strip_tags($update, self::_NETWORK_HTML)));
      if(strlen($update) > self::_NETWORK_LENGTH) {
        throw new LinkedInException('LinkedIn->share(): update length is too long - max length is ' . self::_NETWORK_LENGTH . ' characters.');
      }
      $user   = htmlspecialchars('<a href="' . $profile_url . '">' . $first_name . ' ' . $last_name . '</a>');
  		$data   = '<activity locale="en_US">
    				       <content-type>linkedin-html</content-type>
    				       <body>' . $user . ' ' . $update . '</body>
    				     </activity>';
  
      // send request
      $query    = self::_URL_API . '/v1/people/~/person-activities';
      $response = $this->fetch('POST', $query, $data);
      
      /**
  	   * Check for successful update (a 201 response from LinkedIn server) 
  	   * per the documentation linked in method comments above.
  	   */ 
      return $this->checkResponse(201, $response);
    } else {
      // profile retrieval failed
      throw new LinkedInException('LinkedIn->updateNetwork(): profile data could not be retrieved.');
    }
	}
	
  /**
	 * General network update retrieval function.
	 * 
	 * Takes a string of parameters as input and requests update-related data 
	 * from the Linkedin Network Updates API. See the official documentation for 
	 * $options parameter formatting:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1006
	 * 
	 * For getting more comments, likes, etc, see here:
	 * 
	 *   http://developer.linkedin.com/docs/DOC-1043         	 
	 * 
	 * @param str $options 
	 *         [OPTIONAL] Data retrieval options.
	 * @param str $id 
	 *         [OPTIONAL] The LinkedIn ID to restrict the updates for.
	 *               	 
	 * @return arr
	 *         Array containing retrieval success, LinkedIn response.
	 */
	public function updates($options = NULL, $id = NULL) {
	  // check passed data
    if(!is_null($options) && !is_string($options)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->updates(): bad data passed, $options must be of type string.');
	  }
	  if(!is_null($id) && !is_string($id)) {
	    // bad data passed
		  throw new LinkedInException('LinkedIn->updates(): bad data passed, $id must be of type string.');
	  }
	  
	  // construct and send the request
	  if(!is_null($id) && self::isId($id)) {
	    $query = self::_URL_API . '/v1/people/' . $id . '/network/updates' . trim($options);
	  } else {
      $query = self::_URL_API . '/v1/people/~/network/updates' . trim($options);
    }
	  $response = $this->fetch('GET', $query);
	  
	  /**
	   * Check for successful request (a 200 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
	  return $this->checkResponse(200, $response);
	}
	
	/**
	 * Converts passed XML data to an array.
	 * 
	 * @param str $xml 
	 *         The XML to convert to an array.
	 *            	 
	 * @return arr 
	 *         Array containing the XML data.     
	 * @return bool 
	 *         FALSE if passed data cannot be parsed to an array.     	 
	 */
	public static function xmlToArray($xml) {
	  // check passed data
    if(!is_string($xml)) {
	    // bad data possed
      throw new LinkedInException('LinkedIn->xmlToArray(): bad data passed, $xml must be a non-zero length string.');
	  }
	  
	  $parser = xml_parser_create();
	  xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, 0);
    xml_parser_set_option($parser, XML_OPTION_SKIP_WHITE, 1);
    if(xml_parse_into_struct($parser, $xml, $tags)) {
	    $elements = array();
      $stack    = array();
      foreach($tags as $tag) {
        $index = count($elements);
        if($tag['type'] == 'complete' || $tag['type'] == 'open') {
          $elements[$tag['tag']]               = array();
          $elements[$tag['tag']]['attributes'] = (array_key_exists('attributes', $tag)) ? $tag['attributes'] : NULL;
          $elements[$tag['tag']]['content']    = (array_key_exists('value', $tag)) ? $tag['value'] : NULL;
          if($tag['type'] == 'open') {
            $elements[$tag['tag']]['children'] = array();
            $stack[count($stack)] = &$elements;
            $elements = &$elements[$tag['tag']]['children'];
          }
        }
        if($tag['type'] == 'close') {
          $elements = &$stack[count($stack) - 1];
          unset($stack[count($stack) - 1]);
        }
      }
      $return_data = $elements;
	  } else {
	    // not valid xml data
	    $return_data = FALSE;
	  }
	  xml_parser_free($parser);
    return $return_data;
  }
}

?>