“exec() has been disabled for security reasons” & “Undefined variable”

I found a cool MySQL backup script. It's working fine on some hosting companies. Now I'm trying it on a different host running PHP Version 5.2.8.

I have a php.ini file that contains this (in both root dir and current dir):

disable_functions =. 

I'm getting these warnings, and it seems like they are more than warnings. If exec() doesn't run, the database is not backed-up.

Undefined variable: output in /home/nealsent/public_html/backups/backup_dbs.php on line 21
Undefined variable: res in /home/nealsent/public_html/backups/backup_dbs.php on line 210
exec() has been disabled for security reasons in /home/nealsent/public_html/backups/backup_dbs.php on line 210

The code is the following one.

// dump db
unset($output);

    // Line 210:
exec("$MYSQL_PATH/mysqldump $db_auth --opt $db 2>&1 >$BACKUP_TEMP/$db.sql", $output, $res);