20.2     Before we begin

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If you are still reading, you're hopefully all set to write your own PHP extension. Extension writing in PHP is actually fairly easy, because the PHP team have put a lot of work into making the process as streamlined and fool-proof as possible. Furthermore, as you will discover, the Zend Engine is a remarkable piece of software that really takes much of the hard work away from programmers. You will need to have the PHP source code on your system, and be able to compile it.

For the purpose of this chapter, we're first going to implement a very simple extension that prints out "Hello from extensions!", but then we'll move on to a custom extension that implements factorial calculations. Factorial calculation - as a mathematical function - really stands to benefit a lot from conversion to C.

While working through this chapter, please be aware that porting code from PHP to C can often give a huge performance boost to your applications, but you need to be careful - switching to C makes it much easier to shoot yourself in the foot, or, worse, shoot your whole leg off!