PHP memory_limit locked to 256MB?

Question

I am trying to set memory_limit to 512M, but it's locekd to 256M.

ini_set('memory_limit','512M');
ini_get('memory_limit');    //> Returns: 256M

I have full control on my server. (it's a dedicated)

Please note that everything under 512M works.

ini_set('memory_limit','16M');
ini_get('memory_limit');    //> Returns: 16M

Solution

I found out why. in php.ini I had memory_limit = 256M. Maybe this is considered as an upper limit

Answer 1

3 possibles I can think of / find:

Prior to PHP 5.2.1, in order to use this directive it had to be enabled at compile time by using --enable-memory-limit in the configure line.

OR

The issue detailed here: ini_set("memory_limit") in PHP 5.3.3 is not working at all

OR

ini_set is disabled