Programming PHP

Fleshing Out the Skeleton
The rot13.c file contains the C code that implements the extension. After including a
standard collection of header files, the first important part of the extension is:
/* {{{ rot13_functions[]
*
* every user-visible function must have an entry in rot13_functions[]
*/
function_entry rot13_functions[] = {
PHP_FE(confirm_rot13_compiled, NULL) /* for testing; remove later */
PHP_FE(rot13, NULL)
{NULL, NULL, NULL} /* must be the last line in rot13_functions[] */
};
/* }}} */
The {{{ and }}} sequences in the comments don’t have meaning to the C compiler or
PHP—they indicate a “fold” to editors that understand text folding. If your editor
supports it (Vim6 and Emacs do), you can represent a block of text (e.g., a function
definition) with a single line (e.g., a description of the function). This makes it easier
to edit large files.
The important part in this code is the function_entry array, which lists the uservisible
functions that this extension implements. Two such functions are shown
here. The ext_skel tool generated the confirm_rot13_compiled( ) function for the purposes
of testing. The rot13( ) function came from the definition in rot13.def.
PHP_FE( ) is a macro that stands for PHP Function Entry. The PHP API has many
such convenience macros. While they speed up development for programmers experienced
with the API, they add to the learning curve for beginners.
Next comes the zend_module_entry struct:
zend_module_entry rot13_module_entry = {
STANDARD_MODULE_HEADER,
"rot13",
rot13_functions,
PHP_MINIT(rot13),
PHP_MSHUTDOWN(rot13),
PHP_RINIT(rot13), /* replace with NULL if no request init code */
PHP_RSHUTDOWN(rot13), /* replace with NULL if no request shutdown code */
PHP_MINFO(rot13),
"0.1", /* replace with version number for your extension */
STANDARD_MODULE_PROPERTIES
};
This defines the functions to be called for the various stages of startup and shutdown.
Like most extensions, rot13 doesn’t need per-request startup and shutdown
functions, so follow the instructions in the comments and replace PHP_RINIT(rot13)
and PHP_RSHUTDOWN(rot13) with NULL. The resulting zend_module_entry struct looks
like this:
322 | Chapter 14: Extending PHP
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