【混ぜるな！危険】mysql_connectとPDOを併用した場合、トランザクションが機能しないです

gistfile1.aw

<?php

/*
CREATE TABLE `transaction_test` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL DEFAULT '',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
*/

$connection1 = mysql_connect('localhost', 'root', 'root');
mysql_select_db('test');

$pdo = new PDO("mysql:host=localhost; dbname=test", "root", "root");

mysql_query('BEGIN');
mysql_query("INSERT INTO transaction_test SET name = 'via mysql_connect'");
$pdo->query("INSERT INTO transaction_test SET name = 'via PDO'");
mysql_query('ROLLBACK');

$result = mysql_query('SELECT * FROM transaction_test');

while ( $row = mysql_fetch_array($result, MYSQL_ASSOC) )
{
	var_dump($row);
}
/*
array(2) {
  ["id"]=>
  string(1) "2"
  ["name"]=>
  string(7) "via PDO"
}
*/

mysql_close($connection1);