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   1  <?php
   2  /**
   3   * WordPress Post Thumbnail Template Functions.
   4   *
   5   * Support for post thumbnails
   6   * Themes function.php must call add_theme_support( 'post-thumbnails' ) to use these.
   7   *
   8   * @package WordPress
   9   * @subpackage Template
  10   */
  11  
  12  /**
  13   * Check if post has an image attached.
  14   *
  15   * @since 2.9.0
  16   *
  17   * @param int $post_id Optional. Post ID.
  18   * @return bool Whether post has an image attached.
  19   */
  20  function has_post_thumbnail( $post_id = null ) {
  21      return (bool) get_post_thumbnail_id( $post_id );
  22  }
  23  
  24  /**
  25   * Retrieve Post Thumbnail ID.
  26   *
  27   * @since 2.9.0
  28   *
  29   * @param int $post_id Optional. Post ID.
  30   * @return int
  31   */
  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 );
  35  }
  36  
  37  /**
  38   * Display Post Thumbnail.
  39   *
  40   * @since 2.9.0
  41   *
  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.
  44   */
  45  function the_post_thumbnail( $size = 'post-thumbnail', $attr = '' ) {
  46      echo get_the_post_thumbnail( null, $size, $attr );
  47  }
  48  
  49  /**
  50   * Update cache for thumbnails in the current loop
  51   *
  52   * @since 3.2
  53   *
  54   * @param object $wp_query Optional. A WP_Query instance. Defaults to the $wp_query global.
  55   */
  56  function update_post_thumbnail_cache( $wp_query = null ) {
  57      if ( ! $wp_query )
  58          $wp_query = $GLOBALS['wp_query'];
  59  
  60      if ( $wp_query->thumbnails_cached )
  61          return;
  62  
  63      $thumb_ids = array();
  64      foreach ( $wp_query->posts as $post ) {
  65          if ( $id = get_post_thumbnail_id( $post->ID ) )
  66              $thumb_ids[] = $id;
  67      }
  68  
  69      if ( ! empty ( $thumb_ids ) ) {
  70          _prime_post_caches( $thumb_ids, false, true );
  71      }
  72  
  73      $wp_query->thumbnails_cached = true;
  74  }
  75  
  76  /**
  77   * Retrieve Post Thumbnail.
  78   *
  79   * @since 2.9.0
  80   *
  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.
  84   */
  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
  91          if ( in_the_loop() )
  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 );
  95      } else {
  96          $html = '';
  97      }
  98      return apply_filters( 'post_thumbnail_html', $html, $post_id, $post_thumbnail_id, $size, $attr );
  99  }