How make a SHOW TABLES with PDO

PHP
1

Hello,
I wonder how I can make a SHOW TABLES with PDO.
I tried this but it displays only the first table.

 $allTable = $pdo->query('SHOW TABLES', PDO::FETCH_NUM);
			  foreach($allTable->fetch() as $db=>$tableName) {
                             echo $tableName . '<br />';
         }
2 
$allTable = $this->registry->get('DB')->query('SHOW TABLES');

while($result = $allTable->fetch()) {
     echo $result[0] . '<br />';
}