MySQL Backup, final script !!!

I have been searching inside the mailing lists regarding the a PHP code that dump all or a selected databases from MySQL ... and haven't managed to get a script like PhpMyAdmin does... please any ready script or idea ... <?php exec("mysqldump -u root -ppassword -A > backup.sql"); ?> //Because it didn't work with me (on windows by example). All what I am thinking to do is a script that retrieved the database names then retrieve the tables names, then fields names and dump the data in an schema like mysqldump does.... any suggestions?? Cheers... Nabil