你好@Саша Стефано:

也许我遗漏了什么，但乍一看，你只需要添加一个return 语句（我还没有测试过这段代码，所以如果不是，请告诉我，我会深入研究解决）：

function get_youtube_kod($post_id=null) {
  // Get the post ID if none is provided
  if($post_id==null OR $post_id==\'\') $post_id = get_the_ID();

    // Gets the post\'s content
    $post_array = get_post($post_id); 
    $markup = $post_array->post_content;

    // Checks for a standard YouTube embed
    preg_match(\'#<object[^>]+>.+?http://www.youtube.com/v/([A-Za-z0-9\\-_]+).+?</object>#s\', $markup, $matches);

    // Checks for any YouTube URL
    if(!isset($matches[1])) {
      preg_match(\'#http://w?w?w?.?youtube.com/watch\\?v=([A-Za-z0-9\\-_]+)#s\', $markup, $matches);
    }

    // If no standard YouTube embed is found, checks for one embedded with JR_embed
    if(!isset($matches[1])) {
      preg_match(\'#\\[yt url=([A-Za-z0-9\\-_]+)]#s\', $markup, $matches);
    }

    if(!isset($matches[1])) {
      preg_match(\'#\\[yt url=([A-Za-z0-9\\-_]+)[^>]*]#s\', $markup, $matches);
    }

    // If we\'ve found a YouTube video ID, create the thumbnail URL
    if(isset($matches[1])) {
      $youtube_kod = $matches[1];  
    }
    return $youtube_kod;

};