Q:

Cannot increase memory_limit with ini_set()

I just noticed that I am unable to increase my memory limit above the value configured in php.ini using ini_set(). I can, however, set it to any value below that and increase it to any other value below the one defined in the ini-file.
Does anyone know why this happens or how I could fix it?

A:

This is odd, according to the manual the memory limit can be set anywhere.

Do you have Suhosin installed? With Suhosin, it's possible to impose a global memory limit.
Do you have a .htaccess  file lying around somewhere saying php_value memory_limit xyz?
Do you have Shell Fork Bomb protection activated? It can impose a global memory limit. See the SO question here. (I suppose this could be part of Suhosin).
What does your phpinfo() say concerning "local" and "global" memory_limit values?
How do you specify the limit, can you post a code snippet?

