$dbh = new PDO('MysqL:host=localhost;dbname=test',$user,$pass,array(
    PDO::ATTR_PERSISTENT => true
));

$config = new \Doctrine\DBAL\Configuration();
$connectionParams = array(
    'dbname' => 'mydb','user' => 'user','password' => 'secret','host' => 'localhost','pdo' => $dbh,);
$conn = \Doctrine\DBAL\DriverManager::getConnection($connectionParams,$config);

请务必了解与PDO使用持久连接的含义：What are the disadvantages of using persistent connection in PDO