Creating my own External Module for PHP

Hello, I have a little question to which I hope to find an anwser in here. Currently, I have a big script which receives approx 1.5 million hits every day. Since this script does some common calculations that underlying scripts use, I want to rewrite this into C and initially make it an external module for beta testing and then eventually compile it directly into PHP. Now, I got this really good book, Web Application Development with PHP by Ratschiller and Gerken. It has a complete chapter devoted to "hacking the core of PHP" which shows how to create extensions. Now, they describe 2 common ways of hacking the core... making a shared object (which is what I want at this point) , or compiling the extension right into the core. They decribe how to make your extension with ~/ext/ext_skel , but they don't describe which steps to take when you only want to make a shared object... the only thing they say is "at this point, you should have a new PHP binary or a .so file" ... but they never gave any indication how to chose... they just asume you want a new php binary or sth. Now, can anyone provide me with a few brief description (a few steps) how to make your own dynamically loadable module in PHP? Thanks in advance. Regards, Leon Mergen