PageTemplater.php

<?php


/**
 * Description of PageTemplater
 *
 * @author Nada Alarfag
 *
 * this code is written by Harri Bell-Thomas
 * http://www.wpexplorer.com/wordpress-page-templates-plugin/
 */
class PageTemplater {

    /**
     * A Unique Identifier
     */
    protected $plugin_slug;

    /**
     * A reference to an instance of this class.
     */
    private static $instance;

    /**
     * The array of templates that this plugin tracks.
     */
    protected $templates;

    /**
     * Returns an instance of this class.
     */
    public static function get_instance() {

	if (null == self::$instance) {
	    self::$instance = new PageTemplater();
	}

	return self::$instance;
    }

    /**
     * Initializes the plugin by setting filters and administration functions.
     */
    private function __construct() {

	$this->templates = array();


	// Add a filter to the attributes metabox to inject template into the cache.
	add_filter(
		'page_attributes_dropdown_pages_args', array($this, 'register_project_templates')
	);


	// Add a filter to the save post to inject out template into the page cache
	add_filter(
		'wp_insert_post_data', array($this, 'register_project_templates')
	);


	// Add a filter to the template include to determine if the page has our
	// template assigned and return it's path
	add_filter(
		'template_include', array($this, 'view_project_template')
	);


	// Add your templates to this array.
	$this->templates = array(
	    'Questionnaire-template.php' => 'Questionnaire Template',
	);
    }

    /**
     * Adds our template to the pages cache in order to trick WordPress
     * into thinking the template file exists where it doens't really exist.
     *
     */
    public function register_project_templates($atts) {

	// Create the key used for the themes cache
	$cache_key = 'page_templates-' . md5(get_theme_root() . '/' . get_stylesheet());

	// Retrieve the cache list.
	// If it doesn't exist, or it's empty prepare an array
	$templates = wp_get_theme()->get_page_templates();
	if (empty($templates)) {
	    $templates = array();
	}

	// New cache, therefore remove the old one
	wp_cache_delete($cache_key, 'themes');

	// Now add our template to the list of templates by merging our templates
	// with the existing templates array from the cache.
	$templates = array_merge($templates, $this->templates);

	// Add the modified cache to allow WordPress to pick it up for listing
	// available templates
	wp_cache_add($cache_key, $templates, 'themes', 1800);

	return $atts;
    }

    /**
     * Checks if the template is assigned to the page
     */
    public function view_project_template($template) {

	global $post;

	if (!isset($this->templates[get_post_meta(
				$post->ID, '_wp_page_template', true
			)])) {

	    return $template;
	}

	$file = plugin_dir_path(__FILE__) . get_post_meta(
			$post->ID, '_wp_page_template', true
	);

	// Just to be safe, we check if the file exist first
	if (file_exists($file)) {
	    return $file;
	} else {
	    echo $file;
	}

	return $template;
    }

}

?>