有一点特殊的过滤方式WP_Embed 类，该类将独立链接转换为嵌入的目标：

/**
 * Passes any unlinked URLs that are on their own line to {@link WP_Embed::shortcode()} for potential embedding.
 *
 * @uses WP_Embed::autoembed_callback()
 *
 * @param string $content The content to be searched.
 * @return string Potentially modified $content.
 */
function autoembed( $content ) {
    return preg_replace_callback( \'|^\\s*(https?://[^\\s"]+)\\s*$|im\', array( $this, \'autoembed_callback\' ), $content );
}

add_filter( \'the_content\', \'autoembed_list_items\', 8 );

function autoembed_list_items( $content ) {

    global $wp_embed;

    return preg_replace_callback( \'|<li>(https?://[^\\s"]+)</li>|im\', array( $wp_embed, \'autoembed_callback\' ), $content );
}