从PHP App Engine实例连接到在另一个运行Java Runtime的App Engine中创建的Cloud SQL实例的连接问题

我在连接到App引擎(Java运行时)中托管的Cloud SQL实例时遇到问题.连接客户端是另一个Google应用程序引擎实例中托管的PHP Web应用程序. App Engine实例是否可以连接到另一个实例中的Cloud SQL?

I am experiencing issues connecting to a Cloud SQL instance hosted in an App engine (Java Runtime). The connecting client is a PHP web application hosted in another Google app engine instance. Is it possible for an App engine instance to connect to a Cloud SQL in another instance?

基本上，我的设置如下:

Basically, my setup is as follow:

• Google App Engine 1(Java运行时)
  • 已安装Cloud SQL实例
  • 托管Google端点并在此实例上连接到Cloud SQL
  • Google App Engine 1 (Java Runtime)
    • installed with Cloud SQL instance
    • hosts Google Endpoints and connects to Cloud SQL on this instance
    • 连接到Google App Engine 1的Cloud SQL实例的PHP脚本

    问题是我总是在下面出现错误:

    The problem is I am always getting error below:

    Warning: mysqli_connect(): MySQL server has gone away in /base/data/home/apps/s~some-php-web-app-v1/v1.376456666740733344/includes/database.php on line 29 Warning: mysqli_connect(): Error while reading greeting packet. PID=-1
    

    我认为我的连接代码正确

    I believe that my connection code is correct

    public function connect($server = DBHOST, $username = DBUSER, $password = DBPASS,  $database = DBNAME, $socket = DBSOCKET, $port = DBPORT)
    {
        $this->link = mysqli_connect($server, $username, $password, $database, $port, $socket) or die(mysqli_error());
    }
    

    常量是:

    define('DBHOST', null);
    define('DBSOCKET','/cloudsql/some-app-v1-test:some-db');
    define('DBNAME', 'database_name');
    define('DBUSER', 'root');
    define('DBPORT', null);
    define('DBPASS', null);
    define('PROJECT_PATH', "http:someserver.com//");
    

    这可能吗?如果是这样，我必须设置什么配置才能使其正常工作?

    Is this possible? If it is, what configuration do I have to set in order to make this work?

    谢谢， 斯蒂芬