In PHP which .o file is supposed to contain the knowledge that an extension exists

I'm having problems enabling CURL extension for PHP. The PHP binary has all the necessary curl symbols yet, it does not show as the curl extension is enabled. Can somebody help me find which .o is supposed to contain the knowledge that the curl (or any other) extension exists and enabled? Platform : freebsd. I have tried the option of enabling extensions=curl.so in php.in, it does not help in my case .................................... Thanks Rosh PR