Comment 19 for bug 316441

Just to add as a comment to people suggesting editing php.ini, what you should actually do is edit /etc/php5/conf.d/local.ini, as that will override any php.ini settings without causing configuration conflicts when you next upgrade PHP (apt will warn you that the file you are using differs from that provided by the maintainer).

You can also override PHP values on a per-virtual host basis in Apache.