Problemas para crear una consulta MySQL en Symfony que contenga JOIN y RAND()

$connection = Doctrine_Manager::getConnection()->getDbh(); 

no funcionará... Prueba esto:

$connection = Doctrine_Manager::getInstance()->getCurrentConnection()->getDbh();

Entonces:

$stmt = $connection->query('SELECT * FROM some_table');
$stmt->execute();
$result = $stmt->fetchAll();