Comment 8 for bug 316441

You're probably better off removing the Debian cron job and modifying the php.ini yourself to your prefered settings (even if you revert them back to the original PHP settings).

Unfortunately, it doesn't seam like anyone at Ubuntu is interested in changing this away from the Debian modifications, despite the fact it is non-standard behaviour for PHP.

There is an interesting thread on this somewhere on the PHP internals mailing list, it seams the PHP developers feel the pain of users having problems with distro modified versions of PHP and get quite a few complaints from users because of non-standard mods to the source by the linux distros (obviously not their fault)! Unfortunately couldn't find it now but it's on there somewhere.