try to build a windows extension for php

[enderonmars]

I would like to write a my windows library (dll), and load it from Php.

I took the examples in the php source directories : "php-4.0.4pl1/ext"
They work on linux, but on windows + Visual C++ 6.0, I take the php_modules.dsw, I do the same kind of projetc and I get a library.
But when I start apache I get this message :
Invalid library (maybe not a PHP library) 'php_engine.dll'

any idea would be great !
thanks