Wordpress-当其他用户喜欢他们的帖子时，向他们发送电子邮件

Question

我具有此功能来检查用户何时获得其他用户喜欢的帖子，当他们的帖子被他人喜欢时如何发送电子邮件给帖子作者？

/**
 * Utility to test if the post is already liked
 * @since    0.5
 */
function already_liked( $post_id, $is_comment ) {
    $post_users = NULL;
    $user_id = NULL;
    if ( is_user_logged_in() ) { // user is logged in
        $user_id = get_current_user_id();
        $post_meta_users = ( $is_comment == 1 ) ? get_comment_meta( $post_id, "_user_comment_liked" ) : get_post_meta( $post_id, "_user_liked" );
        if ( count( $post_meta_users ) != 0 ) {
            $post_users = $post_meta_users[0];
        }
    } else { // user is anonymous
        $user_id = sl_get_ip();
        $post_meta_users = ( $is_comment == 1 ) ? get_comment_meta( $post_id, "_user_comment_IP" ) : get_post_meta( $post_id, "_user_IP" ); 
        if ( count( $post_meta_users ) != 0 ) { // meta exists, set up values
            $post_users = $post_meta_users[0];
        }
    }

    if ( is_array( $post_users ) && in_array( $user_id, $post_users ) ) {
        return true;
    } else {
        return false;
    }
} // already_liked()

该帖子供邮政用户喜欢

/**
 * Utility retrieves post meta user likes (user id array), 
 * then adds new user id to retrieved array
 * @since    0.5
 */
function post_user_likes( $user_id, $post_id, $is_comment ) {
    $post_users = '';
    $post_meta_users = ( $is_comment == 1 ) ? get_comment_meta( $post_id, "_user_comment_liked" ) : get_post_meta( $post_id, "_user_liked" );
    if ( count( $post_meta_users ) != 0 ) {
        $post_users = $post_meta_users[0];
    }
    if ( !is_array( $post_users ) ) {
        $post_users = array();
    }
    if ( !in_array( $user_id, $post_users ) ) {
        $post_users['user-' . $user_id] = $user_id;
    }
    return $post_users;
} // post_user_likes()