transaction doesn't work properly

I'm looking for a case how `transaction` do it's job. In first case I write a `sleep(10000)` between two queries, then turn of the wamp server:

PHP Code:

$this->db->trans_begin();
$q1 = $this->db->query("INSERT INTO `test`(`test_col`) VALUES ('aaaaaa')");
sleep(100000);
$q2 = $this->db->query("INSERT INTO `test`(`test_col`) VALUES ('bbbbbb')");
$this->db->trans_complete(); 


But first record is saved without second one. Then I tried with another case, that first query fails because of duplicated value:

PHP Code:

$this->db->trans_begin();
$q1 = $this->db->query("INSERT INTO `test`(`test_col`) VALUES ('duplicated')");
$q2 = $this->db->query("INSERT INTO `test`(`test_col`) VALUES ('new row')");
$this->db->trans_complete(); 


But again the new one exist in the database. Any idea? Is there anything I'm missing?


Also `trans_rollback`  doesn't work.

PHP Code:

if ($this->db->trans_status() === FALSE)
{
    // I get this line, but trans_rollback doesn't work
    $this->db->trans_rollback();
}