public function execute($req, $params = null)
 {
     if (!in_array($req, array('BEGIN', 'COMMIT', 'ROLLBACK'))) {
         if (!$this->autoCommit && !$this->inTransaction) {
             $this->begin();
         }
         if ($params !== null) {
             $req = $this->emuPrepStmt($req, $params);
         }
     }
     return parent::execute($req);
 }