$table1 = new \Models\Table1();
$table2 = new \Models\Table2();

$readConnection = $table1->getReadConnection();

$builder = new \Phalcon\Mvc\Model\Query\Builder();
$builder->from(get_class($table1))
   ->addFrom(get_class($table2), 't2');

echo $readConnection->getDialect()->select($builder->getQuery()->parse());

SELECT `models\Table1`.*, `t2`.* FROM `table1`, `table2` AS `t2`

SELECT `table1`.*, `t2`.* FROM `table1`, `table2` AS `t2`