The only header file you really have to include for your modules is
php.h, located in the PHP directory. This file makes all
macros and API definitions required to build new modules available to your
code.
Tip: It's good practice to create a separate
header file for your module that contains module-specific
definitions. This header file should contain all the forward
definitions for exported functions and include
php.h. If you created your module using
ext_skel you already have such a header file
prepared.
