get-the-image.php

<?php
/**
 * Get the Image - An advanced post image script for WordPress.
 *
 * Get the Image was created to be a highly-intuitive image script that displays post-specific images (an 
 * image-based representation of a post).  The script handles old-style post images via custom fields for 
 * backwards compatibility.  It also supports WordPress' built-in featured image functionality.  On top of 
 * those things, it can automatically set attachment images as the post image or scan the post content for 
 * the first image element used.  It can also fall back to a given default image.
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU 
 * General Public License version 2, as published by the Free Software Foundation.  You may NOT assume 
 * that you can use any other version of the GPL.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without 
 * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * @package GetTheImage
 * @version 0.7.0
 * @author Justin Tadlock <justin@justintadlock.com>
 * @copyright Copyright (c) 2008 - 2011, Justin Tadlock
 * @link http://justintadlock.com/archives/2008/05/27/get-the-image-wordpress-plugin
 * @license http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 */

/* Adds theme support for WordPress 'featured images'. */
add_theme_support( 'post-thumbnails' );

/* Delete the cache when a post or post metadata is updated. */
add_action( 'save_post', array('PPTWJ_Get_The_Image', 'get_the_image_delete_cache_by_post') );
add_action( 'deleted_post_meta', array('PPTWJ_Get_The_Image', 'get_the_image_delete_cache_by_meta'), 10, 2 );
add_action( 'updated_post_meta', array('PPTWJ_Get_The_Image', 'get_the_image_delete_cache_by_meta'), 10, 2 );
add_action( 'added_post_meta', array('PPTWJ_Get_The_Image', 'get_the_image_delete_cache_by_meta'), 10, 2 );

/**
 * The main image function for displaying an image.  It supports several arguments that allow developers to
 * customize how the script outputs the image.
 *
 * The image check order is important to note here.  If an image is found by any specific check, the script
 * will no longer look for images.  The check order is 'meta_key', 'the_post_thumbnail', 'attachment', 
 * 'image_scan', 'callback', and 'default_image'.
 *
 * @since 0.1.0
 * @global $post The current post's database object.
 * @param array $args Arguments for how to load and display the image.
 * @return string|array The HTML for the image. | Image attributes in an array.
 */
function pptwj_get_the_image( $args = array(), $post_id = null ) {
	global $post;

	/* Set the default arguments. */
	$defaults = array(
		'meta_key' => array( 'Thumbnail', 'thumbnail' ),
		'post_id' => is_null( $post_id ) ? $post->ID : $post_id,
		'attachment' => true,
		'the_post_thumbnail' => true, // WP 2.9+ image function
		'size' => 'thumbnail',
		'default_image' => false,
		'order_of_image' => 1,
		'link_to_post' => true,
		'image_class' => false,
		'image_scan' => false,
		'width' => false,
		'height' => false,
		'format' => 'img',
		'meta_key_save' => false,
		'callback' => null,
		'cache' => true,
		'echo' => true,
		'custom_key' => null, // @deprecated 0.6. Use 'meta_key'.
		'default_size' => null, // @deprecated 0.5.  Use 'size'.
	);

	/* Allow plugins/themes to filter the arguments. */
	$args = apply_filters( 'pptwj_get_the_image_args', $args );

	/* Merge the input arguments and the defaults. */
	$args = wp_parse_args( $args, $defaults );

	/* If $default_size is given, overwrite $size. */
	if ( !is_null( $args['default_size'] ) )
		$args['size'] = $args['default_size']; // Deprecated 0.5 in favor of $size

	/* If $custom_key is set, overwrite $meta_key. */
	if ( !is_null( $args['custom_key'] ) )
		$args['meta_key'] = $args['custom_key']; // Deprecated 0.6 in favor of $meta_key

	/* If $format is set to 'array', don't link to the post. */
	if ( 'array' == $args['format'] )
		$args['link_to_post'] = false;

	/* Extract the array to allow easy use of variables. */
	extract( $args );

	/* Get cache key based on $args. */
	$key = md5( serialize( compact( array_keys( $args ) ) ) );

	/* Check for a cached image. */
	$image_cache = wp_cache_get( $post_id, 'pptwj_get_the_image' );

	if ( !is_array( $image_cache ) )
		$image_cache = array();

	/* If there is no cached image, let's see if one exists. */
	if ( !isset( $image_cache[$key] ) || empty( $cache ) ) {

		/* If a custom field key (array) is defined, check for images by custom field. */
		if ( !empty( $meta_key ) )
			$image = PPTWJ_Get_The_Image::get_the_image_by_meta_key( $args );

		/* If no image found and $the_post_thumbnail is set to true, check for a post image (WP feature). */
		if ( empty( $image ) && !empty( $the_post_thumbnail ) )
			$image = PPTWJ_Get_The_Image::get_the_image_by_post_thumbnail( $args );

		/* If no image found and $attachment is set to true, check for an image by attachment. */
		if ( empty( $image ) && !empty( $attachment ) )
			$image = PPTWJ_Get_The_Image::get_the_image_by_attachment( $args );

		/* If no image found and $image_scan is set to true, scan the post for images. */
		if ( empty( $image ) && !empty( $image_scan ) )
			$image = PPTWJ_Get_The_Image::get_the_image_by_scan( $args );

		/* If no image found and a callback function was given. Callback function must pass back array of <img> attributes. */
		if ( empty( $image ) && !is_null( $callback ) && function_exists( $callback ) )
			$image = call_user_func( $callback, $args );

		/* If no image found and a $default_image is set, get the default image. */
		if ( empty( $image ) && !empty( $default_image ) )
			$image = PPTWJ_Get_The_Image::get_the_image_by_default( $args );

		/* If an image was found. */
		if ( !empty( $image ) ) {

			/* If $meta_key_save was set, save the image to a custom field. */
			if ( !empty( $meta_key_save ) )
				PPTWJ_Get_The_Image::get_the_image_meta_key_save( $args, $image['src'] );

			/* Format the image HTML. */
			$image = PPTWJ_Get_The_Image::get_the_image_format( $args, $image );

			/* Set the image cache for the specific post. */
			$image_cache[$key] = $image;
			wp_cache_set( $post_id, $image_cache, 'pptwj_get_the_image' );
		}
	}

	/* If an image was already cached for the post and arguments, use it. */
	else {
		$image = $image_cache[$key];
	}

	/* Allow plugins/theme to override the final output. */
	$image = apply_filters( 'pptwj_get_the_image', $image );

	/* If $format is set to 'array', return an array of image attributes. */
	if ( 'array' == $format ) {

		/* Set up a default empty array. */
		$out = array();

		/* Get the image attributes. */
		$atts = wp_kses_hair( $image, array( 'http' ) );

		/* Loop through the image attributes and add them in key/value pairs for the return array. */
		foreach ( $atts as $att )
			$out[$att['name']] = $att['value'];

		//$out['url'] = $out['src']; // @deprecated 0.5 Use 'src' instead of 'url'.

		/* Return the array of attributes. */
		return $out;
	}

	/* Or, if $echo is set to false, return the formatted image. */
	elseif ( false === $echo ) {
		return $image;
	}

	/* Display the image if we get to this point. */
	echo $image;
}

class PPTWJ_Get_The_Image{

	/* Internal Functions */

	/**
	 * Calls images by custom field key.  Script loops through multiple custom field keys.  If that particular key 
	 * is found, $image is set and the loop breaks.  If an image is found, it is returned.
	 *
	 * @since 0.7.0
	 * @param array $args Arguments for how to load and display the image.
	 * @return array|bool Array of image attributes. | False if no image is found.
	 */
	static function get_the_image_by_meta_key( $args = array() ) {

		/* If $meta_key is not an array. */
		if ( !is_array( $args['meta_key'] ) ) {

			/* Get the image URL by the single meta key. */
			$image = get_post_meta( $args['post_id'], $args['meta_key'], true );
		}

		/* If $meta_key is an array. */
		elseif ( is_array( $args['meta_key'] ) ) {

			/* Loop through each of the given meta keys. */
			foreach ( $args['meta_key'] as $meta_key ) {

				/* Get the image URL by the current meta key in the loop. */
				$image = get_post_meta( $args['post_id'], $meta_key, true );

				/* If an image was found, break out of the loop. */
				if ( !empty( $image ) )
					break;
			}
		}

		/* If a custom key value has been given for one of the keys, return the image URL. */
		if ( !empty( $image ) )
			return array( 'src' => $image );

		return false;
	}

	/**
	 * Checks for images using a custom version of the WordPress 2.9+ get_the_post_thumbnail() function.  
	 * If an image is found, return it and the $post_thumbnail_id.  The WordPress function's other filters are 
	 * later added in the self::display_the_image() function.
	 *
	 * @since 0.7.0
	 * @param array $args Arguments for how to load and display the image.
	 * @return array|bool Array of image attributes. | False if no image is found.
	 */
	static function get_the_image_by_post_thumbnail( $args = array() ) {

		/* Check for a post image ID (set by WP as a custom field). */
		$post_thumbnail_id = get_post_thumbnail_id( $args['post_id'] );

		/* If no post image ID is found, return false. */
		if ( empty( $post_thumbnail_id ) )
			return false;

		/* Apply filters on post_thumbnail_size because this is a default WP filter used with its image feature. */
		$size = apply_filters( 'post_thumbnail_size', $args['size'] );

		/* Get the attachment image source.  This should return an array. */
		$image = wp_get_attachment_image_src( $post_thumbnail_id, $size );

		/* Get the attachment excerpt to use as alt text. */
		$alt = trim( strip_tags( get_post_field( 'post_excerpt', $post_thumbnail_id ) ) );

		/* Return both the image URL and the post thumbnail ID. */
		return array( 'src' => $image[0], 'post_thumbnail_id' => $post_thumbnail_id, 'alt' => $alt );
	}

	/**
	 * Check for attachment images.  Uses get_children() to check if the post has images attached.  If image 
	 * attachments are found, loop through each.  The loop only breaks once $order_of_image is reached.
	 *
	 * @since 0.7.0
	 * @param array $args Arguments for how to load and display the image.
	 * @return array|bool Array of image attributes. | False if no image is found.
	 */
	static function get_the_image_by_attachment( $args = array() ) {

		/* Get attachments for the inputted $post_id. */
		$attachments = get_children( array( 'post_parent' => $args['post_id'], 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => 'ASC', 'orderby' => 'menu_order ID' ) );

		/* If no attachments are found, check if the post itself is an attachment and grab its image. */
		if ( empty( $attachments ) && $args['size'] ) {
			if ( 'attachment' == get_post_type( $args['post_id'] ) ) {
				$image = wp_get_attachment_image_src( $args['post_id'], $args['size'] );
				$alt = trim( strip_tags( get_post_field( 'post_excerpt', $args['post_id'] ) ) );
			}
		}

		/* If no attachments or image is found, return false. */
		if ( empty( $attachments ) && empty( $image ) )
			return false;

		/* Set the default iterator to 0. */
		$i = 0;

		/* Loop through each attachment. Once the $order_of_image (default is '1') is reached, break the loop. */
		foreach ( $attachments as $id => $attachment ) {
			if ( ++$i == $args['order_of_image'] ) {
				$image = wp_get_attachment_image_src( $id, $args['size'] );
				$alt = trim( strip_tags( get_post_field( 'post_excerpt', $id ) ) );
				break;
			}
		}

		/* Return the image URL. */
		return array( 'src' => $image[0], 'alt' => $alt );
	}

	/**
	 * Scans the post for images within the content.  Not called by default with self::get_the_image().  Shouldn't use 
	 * if using large images within posts, better to use the other options.
	 *
	 * @since 0.7.0
	 * @param array $args Arguments for how to load and display the image.
	 * @return array|bool Array of image attributes. | False if no image is found.
	 */
	static function get_the_image_by_scan( $args = array() ) {

		/* Search the post's content for the <img /> tag and get its URL. */
		preg_match_all( '|<img.*?src=[\'"](.*?)[\'"].*?>|i', get_post_field( 'post_content', $args['post_id'] ), $matches );

		/* If there is a match for the image, return its URL. */
		if ( isset( $matches ) && !empty( $matches[1][0] ) )
			return array( 'src' => $matches[1][0] );

		return false;
	}

	/**
	 * Used for setting a default image.  The function simply returns the image URL it was given in an array.  
	 * Not used with self::get_the_image() by default.
	 *
	 * @since 0.7.0
	 * @param array $args Arguments for how to load and display the image.
	 * @return array|bool Array of image attributes. | False if no image is found.
	 */
	static function get_the_image_by_default( $args = array() ) {
		return array( 'src' => $args['default_image'] );
	}

	/**
	 * Formats an image with appropriate alt text and class.  Adds a link to the post if argument is set.  Should 
	 * only be called if there is an image to display, but will handle it if not.
	 *
	 * @since 0.7.0
	 * @param array $args Arguments for how to load and display the image.
	 * @param array $image Array of image attributes ($image, $classes, $alt, $caption).
	 * @return string $image Formatted image (w/link to post if the option is set).
	 */
	static function get_the_image_format( $args = array(), $image = false ) {

		/* If there is no image URL, return false. */
		if ( empty( $image['src'] ) )
			return false;

		/* Extract the arguments for easy-to-use variables. */
		extract( $args );

		/* If there is alt text, set it.  Otherwise, default to the post title. */
		$image_alt = ( ( !empty( $image['alt'] ) ) ? $image['alt'] : apply_filters( 'the_title', get_post_field( 'post_title', $post_id ) ) );

		/* If there is a width or height, set them as HMTL-ready attributes. */
		$width = ( ( $width ) ? ' width="' . esc_attr( $width ) . '"' : '' );
		$height = ( ( $height ) ? ' height="' . esc_attr( $height ) . '"' : '' );

		/* Loop through the custom field keys and add them as classes. */
		if ( is_array( $meta_key ) ) {
			foreach ( $meta_key as $key )
				$classes[] = str_replace( ' ', '-', strtolower( $key ) );
		}

		/* Add the $size and any user-added $image_class to the class. */
		$classes[] = $size;
		$classes[] = $image_class;

		/* Join all the classes into a single string and make sure there are no duplicates. */
		$class = join( ' ', array_unique( $classes ) );

		/* If there is a $post_thumbnail_id, apply the WP filters normally associated with get_the_post_thumbnail(). */
		if ( !empty( $image['post_thumbnail_id'] ) )
			do_action( 'begin_fetch_post_thumbnail_html', $post_id, $image['post_thumbnail_id'], $size );

		/* Add the image attributes to the <img /> element. */
		$html = '<img src="' . $image['src'] . '" alt="' . esc_attr( strip_tags( $image_alt ) ) . '" class="' . esc_attr( $class ) . '"' . $width . $height . ' />';

		/* If $link_to_post is set to true, link the image to its post. */
		if ( $link_to_post )
			$html = '<a href="' . get_permalink( $post_id ) . '" title="' . esc_attr( apply_filters( 'the_title', get_post_field( 'post_title', $post_id ) ) ) . '">' . $html . '</a>';

		/* If there is a $post_thumbnail_id, apply the WP filters normally associated with get_the_post_thumbnail(). */
		if ( !empty( $image['post_thumbnail_id'] ) )
			do_action( 'end_fetch_post_thumbnail_html', $post_id, $image['post_thumbnail_id'], $size );

		/* If there is a $post_thumbnail_id, apply the WP filters normally associated with get_the_post_thumbnail(). */
		if ( !empty( $image['post_thumbnail_id'] ) )
			$html = apply_filters( 'post_thumbnail_html', $html, $post_id, $image['post_thumbnail_id'], $size, '' );

		return $html;
	}

	/**
	 * Saves the image URL as the value of the meta key provided.  This allows users to set a custom meta key 
	 * for their image.  By doing this, users can trim off database queries when grabbing attachments or get rid 
	 * of expensive scans of the content when using the image scan feature.
	 *
	 * @since 0.6.0
	 * @param array $args Arguments for how to load and display the image.
	 * @param array $image Array of image attributes ($image, $classes, $alt, $caption).
	 */
	static function get_the_image_meta_key_save( $args = array(), $image = array() ) {

		/* If the $meta_key_save argument is empty or there is no image $url given, return. */
		if ( empty( $args['meta_key_save'] ) || empty( $image['src'] ) )
			return;

		/* Get the current value of the meta key. */
		$meta = get_post_meta( $args['post_id'], $args['meta_key_save'], true );

		/* If there is no value for the meta key, set a new value with the image $url. */
		if ( empty( $meta ) )
			add_post_meta( $args['post_id'], $args['meta_key_save'], $image['src'] );

		/* If the current value doesn't match the image $url, update it. */
		elseif ( $meta !== $image['src'] )
			update_post_meta( $args['post_id'], $args['meta_key_save'], $image['src'], $meta );
	}

	/**
	 * Deletes the image cache for the specific post when the 'save_post' hook is fired.
	 *
	 * @since 0.7.0
	 */
	static function get_the_image_delete_cache_by_post( $post_id ) {
		wp_cache_delete( $post_id, 'pptwj_get_the_image' );
	}

	/**
	 * Deletes the image cache for a specific post when the 'added_post_meta', 'deleted_post_meta', 
	 * or 'updated_post_meta' hooks are called.
	 *
	 * @since 0.7.0
	 */
	static function get_the_image_delete_cache_by_meta( $meta_id, $post_id ) {
		wp_cache_delete( $post_id, 'pptwj_get_the_image' );
	}

	/**
	 * @since 0.1.0
	 * @deprecated 0.3.0
	 */
	static function get_the_image_link( $deprecated = '', $deprecated_2 = '', $deprecated_3 = '' ) {
		self::get_the_image();
	}

	/**
	 * @since 0.3.0
	 * @deprecated 0.7.0
	 */
	static function image_by_custom_field( $args = array() ) {
		return self::get_the_image_by_meta_key( $args );
	}

	/**
	 * @since 0.4.0
	 * @deprecated 0.7.0
	 */
	static function image_by_the_post_thumbnail( $args = array() ) {
		return self::get_the_image_by_post_thumbnail( $args );
	}

	/**
	 * @since 0.3.0
	 * @deprecated 0.7.0
	 */
	static function image_by_attachment( $args = array() ) {
		return self::get_the_image_by_attachment( $args );
	}

	/**
	 * @since 0.3.0
	 * @deprecated 0.7.0
	 */
	static function image_by_scan( $args = array() ) {
		return self::get_the_image_by_scan( $args );
	}

	/**
	 * @since 0.3.0
	 * @deprecated 0.7.0
	 */
	static function image_by_default( $args = array() ) {
		return self::get_the_image_by_default( $args );
	}

	/**
	 * @since 0.1.0
	 * @deprecated 0.7.0
	 */
	static function display_the_image( $args = array(), $image = false ) {
		return self::get_the_image_format( $args, $image );
	}

	/**
	 * @since 0.5.0
	 * @deprecated 0.7.0 Replaced by cache delete functions specifically for the post ID.
	 */
	static function get_the_image_delete_cache() {
		return;
	}

}//PPTWJ_Get_The_Image class

?>