3 * WordPress Post Thumbnail Template Functions.
5 * Support for post thumbnails
6 * Themes function.php must call add_theme_support( 'post-thumbnails' ) to use these.
13 * Check if post has an image attached.
17 * @param int $post_id Optional. Post ID.
18 * @return bool Whether post has an image attached.
20 function has_post_thumbnail( $post_id = null ) {
21 return (bool) get_post_thumbnail_id( $post_id );
25 * Retrieve Post Thumbnail ID.
29 * @param int $post_id Optional. Post ID.
32 function get_post_thumbnail_id( $post_id = null ) {
33 $post_id = ( null === $post_id ) ? get_the_ID() : $post_id;
34 return get_post_meta( $post_id, '_thumbnail_id', true );
38 * Display Post Thumbnail.
42 * @param int $size Optional. Image size. Defaults to 'post-thumbnail', which theme sets using set_post_thumbnail_size( $width, $height, $crop_flag );.
43 * @param string|array $attr Optional. Query string or array of attributes.
45 function the_post_thumbnail( $size = 'post-thumbnail', $attr = '' ) {
46 echo get_the_post_thumbnail( null, $size, $attr );
50 * Update cache for thumbnails in the current loop
54 * @param object $wp_query Optional. A WP_Query instance. Defaults to the $wp_query global.
56 function update_post_thumbnail_cache( $wp_query = null ) {
58 $wp_query = $GLOBALS['wp_query'];
60 if ( $wp_query->thumbnails_cached )
64 foreach ( $wp_query->posts as $post ) {
65 if ( $id = get_post_thumbnail_id( $post->ID ) )
69 if ( ! empty ( $thumb_ids ) ) {
70 _prime_post_caches( $thumb_ids, false, true );
73 $wp_query->thumbnails_cached = true;
77 * Retrieve Post Thumbnail.
81 * @param int $post_id Optional. Post ID.
82 * @param string $size Optional. Image size. Defaults to 'post-thumbnail'.
83 * @param string|array $attr Optional. Query string or array of attributes.
85 function get_the_post_thumbnail( $post_id = null, $size = 'post-thumbnail', $attr = '' ) {
86 $post_id = ( null === $post_id ) ? get_the_ID() : $post_id;
87 $post_thumbnail_id = get_post_thumbnail_id( $post_id );
88 $size = apply_filters( 'post_thumbnail_size', $size );
89 if ( $post_thumbnail_id ) {
90 do_action( 'begin_fetch_post_thumbnail_html', $post_id, $post_thumbnail_id, $size ); // for "Just In Time" filtering of all of wp_get_attachment_image()'s filters
92 update_post_thumbnail_cache();
93 $html = wp_get_attachment_image( $post_thumbnail_id, $size, false, $attr );
94 do_action( 'end_fetch_post_thumbnail_html', $post_id, $post_thumbnail_id, $size );
98 return apply_filters( 'post_thumbnail_html', $html, $post_id, $post_thumbnail_id, $size, $attr );