An introduction to PHP extension development

PHP (Hypertext Preprocessor) is one of the most widely used programming languages ​​for web development. Its flexibility and large developer community have made it a popular choice for creating dynamic and interactive web applications. However, there are situations where the native functionality of PHP may not be enough, or where performance can be improved. In these cases, developing a PHP extension can be an effective solution. This article provides an introduction to PHP extension development, exploring the reasons why you might need one and the basic steps to create one.

There are several reasons why a developer might decide to create a PHP extension:

1. Performance: PHP extensions are written in C, a high-performance programming language. This means that they can perform complex operations much faster than pure PHP code.

2. Additional functionality: If PHP does not natively support a feature you need, an extension can fill this gap.

3. Interfacing with third-party libraries: Some external libraries or APIs can be integrated directly into PHP through an extension, allowing for tighter and more efficient interaction.

Before starting with the development of a PHP extension, you should have a good understanding of:

• PHP: Advanced knowledge of the language and its ecosystem.
• C: Since extensions are written in C, familiarity with this language is essential.
• Development tools: GCC (GNU Compiler Collection), Autotools, and other utilities for compiling and debugging code C.

To develop extensions, you need to have PHP and its development libraries installed. On Debian-based systems, this can be done with:

sudo apt-get install php php-dev

Then make sure you have GCC and Make installed:

sudo apt-get install build-essential

To illustrate the process, let's create a simple extension that adds a custom function to PHP. Let's first create a directory for the project.

mkdir my_extension
cd my_extension

Now let's create a configuration file config.m4 that tells PHP how to compile the extension.

PHP_ARG_ENABLE(my_extension, whether to enable my_extension support,
[ --enable-my_extension Enable my_extension support])

if test "$PHP_MY_EXTENSION" != "no"; then
    PHP_NEW_EXTENSION(my_extension, my_extension.c, $ext_shared)
fi

Then we create the source file my_extension.c which contains the C code for the extension.

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "php.h"

// Function declaration
PHP_FUNCTION(hello_world) {
    php_printf("Hello, World!\n");
}

// Definition of available functions
const zend_function_entry my_extension_functions[] = {
    PHP_FE(hello_world, NULL)
    PHP_FE_END
};

// Module entry point
zend_module_entry my_extension_module_entry = {
    STANDARD_MODULE_HEADER,
    "my_extension",
    my_extension_functions,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NO_VERSION_YET,
    STANDARD_MODULE_PROPERTIES
};

ZEND_GET_MODULE(my_extension)

We run the following commands to configure and compile the extension:

phpize
./configure --enable-my_extension
make
sudo make install

After compiling and installing the extension, you need to enable it in the PHP configuration file (php.ini):

extension=my_extension.so

To verify that the extension has been correctly installed and enabled, we create a PHP script and call the defined function:

<?php
hello_world();

Let's run the script with:

php test.php

If everything has been correctly configured, it should print "Hello, World!".

Conclusion

Developing extensions for PHP may seem like a complex task, but with a good understanding of PHP and C, you can create powerful extensions that improve performance and add functionality to your PHP environment. This article has provided an overview of the steps needed to get started, but there are many other resources and documentation available to further delve into this fascinating topic.