[WDDX]--Try to compil --enable-wddx

Hi ! I'm a developper but not a sys admin but today i must be it in order to configure PHP with wddx extension...but i don't know where i must type "./configue --enable-wddx" on my mandrake 9.0 server...where is the php folder ? (find -name...give me no great response)...must i do that on php folder or apache folder ? Note : It's a PHP4.2.3 installed by default with my mandrake...so i never need to compil it before... thx a lot for u answers... Great, Stef.