PHP + MySQL transactions examples

I really haven't found normal example of PHP file where MySQL transactions are being used. Can you show me simple example of that? And one more question. I've already done a lot of programming and didn't use transactions. Can I put a PHP function or something in `header.php` that if one `mysql_query` fails, then the others fail too? --- I think I have figured it out, is it right?: mysql_query("SET AUTOCOMMIT=0"); mysql_query("START TRANSACTION"); $a1 = mysql_query("INSERT INTO rarara (l_id) VALUES('1')"); $a2 = mysql_query("INSERT INTO rarara (l_id) VALUES('2')"); if ($a1 and $a2) { mysql_query("COMMIT"); } else { mysql_query("ROLLBACK"); }