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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 (true) or not (false).
  19   */
  20  function has_post_thumbnail( $post_id = NULL ) {
  21      global $id;
  22      $post_id = ( NULL === $post_id ) ? $id : $post_id;
  23      return !! get_post_thumbnail_id( $post_id );
  24  }
  25  
  26  /**
  27   * Retrieve Post Thumbnail ID.
  28   * 
  29   * @since 2.9.0
  30   *
  31   * @param int $post_id Optional. Post ID.
  32   * @return int
  33   */
  34  function get_post_thumbnail_id( $post_id = NULL ) {
  35      global $id;
  36      $post_id = ( NULL === $post_id ) ? $id : $post_id;
  37      return get_post_meta( $post_id, '_thumbnail_id', true );
  38  }
  39  
  40  /**
  41   * Display Post Thumbnail.
  42   * 
  43   * @since 2.9.0
  44   *
  45   * @param int $size Optional. Image size.  Defaults to 'post-thumbnail', which theme sets using set_post_thumbnail_size( $width, $height, $crop_flag );.
  46   * @param string|array $attr Optional. Query string or array of attributes.
  47   */
  48  function the_post_thumbnail( $size = 'post-thumbnail', $attr = '' ) {
  49      echo get_the_post_thumbnail( NULL, $size, $attr );
  50  }
  51  
  52  /**
  53   * Retrieve Post Thumbnail.
  54   * 
  55   * @since 2.9.0
  56   *
  57   * @param int $post_id Optional. Post ID.
  58   * @param string $size Optional. Image size.  Defaults to 'thumbnail'.
  59   * @param string|array $attr Optional. Query string or array of attributes.
  60    */
  61  function get_the_post_thumbnail( $post_id = NULL, $size = 'post-thumbnail', $attr = '' ) {
  62      global $id;
  63      $post_id = ( NULL === $post_id ) ? $id : $post_id;
  64      $post_thumbnail_id = get_post_thumbnail_id( $post_id );
  65      $size = apply_filters( 'post_thumbnail_size', $size );
  66      if ( $post_thumbnail_id ) {
  67          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
  68          $html = wp_get_attachment_image( $post_thumbnail_id, $size, false, $attr );
  69          do_action( 'end_fetch_post_thumbnail_html', $post_id, $post_thumbnail_id, $size );
  70      } else {
  71          $html = '';
  72      }
  73      return apply_filters( 'post_thumbnail_html', $html, $post_id, $post_thumbnail_id, $size, $attr );
  74  }
  75  
  76  ?>