The Apache programming interface

The the Apache Web server's application program interface (API) is a structure arrangement on the C implementation language level. If you want to write a module for Apache, then you have to define your own global API structures in your own source code, which make a connection to the Web server's kernel during the compilation procedure. At runtime, these structures define a range of jump in points, so-called API hooks. If a programmer wants to make the Apache kernel call up a function he has developed for rewriting a URL to a file name, for example, he registers this function with the hook "URL-to-filename", as in mod_rewrite, for example.

Apache currently recognises eight hooks, which are processed in sequence in the course of completing a browser request. With each of these jump in points, the kernel calls up all the modules which have been registered for this hook.

The sequence of calls is dependent on which position the modules take in the configuration. The Web master creates this file before compiling the Web server or adapts it to his own needs.

The Apache API specification can be examined at http://www.apache.org/docs/misc/API.html.