在Openshift上从Zend_Db连接到MySQL时出现PDO错误

I get this problem when I try to connect from Zend_Db to MySQL on OpenShift:

Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000] [2002] Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)' in /var/lib/openshift/52e2f054e0b8cd9dba000122/app-root/runtime/repo/library/Zend/Controller/Plugin/Broker.php on line 336 PDOException: SQLSTATE[HY000] [2002] Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2) in /var/lib/openshift/52e2f054e0b8cd9dba000122/app-root/runtime/repo/library/Zend/Db/Adapter/Pdo/Abstract.php on line 129

I have tried to enter the values from the relevant Env. variables that Openshift creates in the application.ini:

resources.db.adapter = "PDO_MYSQL"
resources.db.isdefaulttableadapter = true
resources.db.params.dbname = "XXXX"
resources.db.params.username = "XXXX"
resources.db.params.password = "XXXX"
resources.db.params.hostname = "127.5.203.2"
resources.db.params.charset = "UTF8"

I have also tried this in a .htaccess file:

php_value mysql.default_socket "${OPENSHIFT_MYSQL_DB_SOCKET}"
php_value mysqli.default_socket "${OPENSHIFT_MYSQL_DB_SOCKET}"

also in the index.php file with:

 $openshiftsocket = getenv('OPENSHIFT_MYSQL_DB_SOCKET');
    //echo "OpenShift socket is [$openshiftsocket]";

    if (isset($openshiftsocket)) {
       echo 'foo';
       ini_set('mysql.default_socket', $openshiftsocket);
       ini_set('mysqli.default_socket', $openshiftsocket);
    }

But I keep getting the error.