调用未定义的函数'ini_set'

Does anybody know how to debug "call to undefined function init_set" , when trying to change php.ini configuration settings programmatically? I am just trying to call init_set function in the code, and the apache couldn't process it at that line.

I recently installed my Apache 2.2 on my Windows XP machine, along with php 5.2 as well.

I tried googling and searching stackoverflow for this but I couldn't find the answer I was looking for.

Could anybody shed some light on it?

it's ini_set not init_set (check http://php.net/ini_set)