How to create custom PHP extension?

Required Tools

In order to create custom PHP extension, requires the following build tools

• A C/C++ compiler (For example, GCC).
• phpize which is a shell script to prepare PHP extension for compiling.
• php-config which is a simple shell script for obtaining information about the installed PHP configuration.

On RPM based systems, required packages can be installed using following command:

$ yum install gcc php php-devel

On Debian based systems, required packages can be installed using following command:

$ apt-get install gcc php php5-dev

Create config.m4 file 

PHP_ARG_ENABLE(my_extension, whether to enable my extension, 

[ --enable-my-extension Enable my extension])

if test "$PHP_MY_EXTENSION" = "yes"; then

 AC_DEFINE(HAVE_MY_EXTENSION, 1, [Whether you have my extension])

 PHP_NEW_EXTENSION(my_extension, my_custom_extension.c, $ext_shared)

fi

The config.m4 file for an extension tells the UNIX build system 

• what configure options your extension supports
• what external libraries and includes you require
• what source your require

This config.m4 stores the basic configuration data used by the PHP 

to compile your custom extension.

Create my_custom_extension.c 

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "php.h"

#define PHP_MY_EXTENSION_VERSION "1.0"

#define PHP_MY_EXTENSION_EXTNAME "my_extension"

extern zend_module_entry my_extension_module_entry;

#define phpext_my_extension_ptr &my_extension_module_entry

// declaration of a custom my_function()

PHP_FUNCTION(my_function);

// list of custom PHP functions provided by this extension

// set {NULL, NULL, NULL} as the last record to mark the end of list

static function_entry my_functions[] = {

PHP_FE(my_function, NULL)

{NULL, NULL, NULL}};

// the following code creates an entry for the module and registers it with Zend.

zend_module_entry my_extension_module_entry = {

#if ZEND_MODULE_API_NO >= 20010901

STANDARD_MODULE_HEADER,

#endif

PHP_MY_EXTENSION_EXTNAME,

my_functions,

NULL, // name of the MINIT function or NULL if not applicable

NULL, // name of the MSHUTDOWN function or NULL if not applicable

NULL, // name of the RINIT function or NULL if not applicable

NULL, // name of the RSHUTDOWN function or NULL if not applicable

NULL, // name of the MINFO function or NULL if not applicable

#if ZEND_MODULE_API_NO >= 20010901

PHP_MY_EXTENSION_VERSION,

#endif

STANDARD_MODULE_PROPERTIES

};

ZEND_GET_MODULE(my_extension)

// implementation of a custom my_function()

PHP_FUNCTION(my_function) {

RETURN_STRING("A line from my custom php extension", 1);

}

Building the extension

$ phpize

$ ./configure

$ make install

• The phpize command will generate additional configuration  files, required to compile your PHP extension 
• you can reverse this process anytime by typing the “phpize –clean” command
• After running each of these commands, you should have a my_custom_extension.so file in PHP extensions directory.

If don’t know the name of that directory, you can check it’s name by typing:

$ php-config | grep extension-dir

Configure php.ini

The last thing you need to do, is to add the following line to your php.ini to load your extension on PHP startup:

extension=my_extension.so

Testing the extension

You can test your PHP extension by typing the following command: $ php -r "echo my_function();"

If everything was fine, the output will be: A line from my custom php extension