Building PHP for extension development
Talking to the UNIX build system: config.m4
The PHP 5 build system
PHP Manual

## The ext_skel script

A PHP extension is composed of several files common to all extensions. As the details of many of those files are similar from extension to extension, it can be laborious to duplicate the content for each one. Fortunately, there is a script which can do all of the initial setup for you. It's called ext_skel, and it's been distributed with PHP since 4.0.

Running ext_skel with no parameters produces this output in PHP 5.2.2:

    php-5.2.2/ext$ ./ext_skel
    ./ext_skel --extname=module [--proto=file] [--stubs=file] [--xml[=file]]
               [--skel=dir] [--full-xml] [--no-help]

      --extname=module   module is the name of your extension
      --proto=file       file contains prototypes of functions to create
      --stubs=file       generate only function stubs in file
      --xml              generate xml documentation to be added to phpdoc-cvs
      --skel=dir         path to the skeleton directory
      --full-xml         generate xml documentation for a self-contained extension
                         (not yet implemented)
      --no-help          don't try to be nice and create comments in the code
                         and helper functions to test if the module compiled

Generally, when developing a new extension the only parameters you will be interested in are --extname and --no-help. Unless you are already experienced with the structure of an extension, you will not want to use --no-help; specifying it causes ext_skel to leave out many helpful comments in the files it generates.

This leaves you with --extname, which tells ext_skel what the name of your extension is. This "name" is an all-lowercase identifier containing only letters and underscores which is unique among everything in the ext/ folder of your PHP distribution.

The --proto option is intended to allow the developer to specify a header file from which a set of PHP functions will be created, ostensibly for the purpose of developing an extension based on a library, but it often functions poorly with most modern header files. A test run on the zlib.h header resulted in a very large number of empty and nonsense prototypes in the ext_skel output files. The --xml and --full-xml options are entirely nonfunctional thus far. The --skel option can be used to specify a modified set of skeleton files to work from, a topic which is beyond the scope of this section.