Add Spice to Your PHP Programs

If you develop data driven websites then there are certain things you have to
repeat. For instance, for each and every transaction with the database, you have
to create a connection, log on to it, perform certain transactions and then
disconnect. This not only consumes a lot of your precious time, but also
efforts. You can automate this task by creating custom extensions in PHP.

Extensions can be considered as plug-ins for the PHP engine or simply as an
add-on. They are written mostly in C language and due to this, you can write
processor intensive functions in C and they will work faster than functions that
have been written in PHP. Other than this, suppose you have a code that is
required frequently, you can include this piece of code as an extension rather
than calling it as a function. This makes it faster and more efficient. You can
also use extension in scenarios when you don't want to provide your source code.
Just make an extension and give it away to the devel- oper, but ofcourse with
the necessary documentation.

Prerequisites

PHP has three kinds of extensions: ZEND engine, built-in and external. In
this article we will create a 'built-in' extension. This is compiled with PHP
and gets loaded along with other PHP processes. Before you can start developing
custom extensions, you need to load PHP and Apache on your workstation. We built
them on a Fedora 7 Linux machine, so the command to install them is as follows:

# yum -y install httpd php mysql mysql-server php-mysql

This command not only installs PHP and Apache, but it also installs MySQL
Server and further integrates PHP and MySQL. However, remember that in order to
run these commands, an Internet connection is a must, because these commands
have to download certain required files.

Custom built module, which gets loaded with PHP can be viewed under the 'Additional Modules' section

Building a Custom Extension

Let's begin by adding a simple 'hello' extension to PHP. For this you have
to make three different files:

1. First is the source file where the source code will reside,

2. Second is the configuration file which will be required by 'phpize' for
building up the extension. 'phpize' is basically a shell script, which is
required for preparing PHP extensions for compilation.

3. Third is the header file which has references that will be required by PHP
for loading the extensions. In order to avoid any mess-up, let us give the test
directory a name 'hello'.

Now, we will write a simple source code, which will contain the description for
the function 'hello_world()'. Name the file created as 'hello.c'. The source
code for the same is written below:

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "php.h"

#include "php_hello.h"

static function_entry hello_functions<> = {

PHP_FE(hello_world, NULL)

{NULL, NULL, NULL}

};

zend_module_entry hello_module_entry = {

#if ZEND_MODULE_API_NO >= 20010901

STANDARD_MODULE_HEADER,

#endif

PHP_HELLO_WORLD_EXTNAME,

hello_functions,

NULL,

NULL,

NULL,

NULL,

NULL,

#if ZEND_MODULE_API_NO >= 20010901

PHP_HELLO_WORLD_VERSION,

#endif

STANDARD_MODULE_PROPERTIES

};

#ifdef COMPILE_DL_HELLO

ZEND_GET_MODULE(hello)

#endif

PHP_FUNCTION(hello_world)

{

RETURN_STRING("Hello World", 1);

}

Similarly, create the header file, and name it 'php_hello.h'. The source code
required for creating the header is

written below.

#ifndef PHP_HELLO_H

#define PHP_HELLO_H 1

#define PHP_HELLO_WORLD_VERSION "1.0"

#define PHP_HELLO_WORLD_EXTNAME "hello"

PHP_FUNCTION(hello_world);

extern zend_module_entry hello_module_entry;

#define phpext_hello_ptr &hello_module_entry

#endif

Now, create the configuration file, and name it config.m4. The creation of
the configuration file includes the

following code:

PHP_ARG_ENABLE(hello, whether to enable Hello World
support,

< --enable-hello Enable Hello World support>)

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

AC_DEFINE(HAVE_HELLO, 1, )

PHP_NEW_EXTENSION(hello, hello.c, $ext_shared)

fi

Finally, to build an extension run the following commands:

# phpize

# ./configure --enable-hello

# make

Once you are through with all these steps, a 'hello.so' file will be generated
in the module directory inside the 'hello' folder. To check whether the
extension you created gets loaded along with PHP, open Internet Explorer, load a
test Web page showing 'phpinfo(),' and look into additional modules. It will
display the extension name 'hello' there. You can also use 'extended_ loaded()'
function to view the loaded extension.

Use 'extension_loaded()' function to view more details of the extension that you load. The details would be similar to what is shown in the screenshot above