Follow these simple steps to install PHP on Windows. You must install Apache2 before installing PHP, See my other tutorial on How to Install apache on Windows

Step 1: Download PHP 5
Download the latest PHP 5 ZIP package from www.php.net/downloads.php

Step 2: Extract the files
We will install the PHP files to C:\php, so create that folder and extract the contents of the ZIP file into it.

PHP can be installed anywhere on your system, but you will need to change the paths referenced in the following steps.

Step 3: Configure php.ini
Copy C:\php\php.ini-recommended to C:\php\php.ini. There are several lines you will need to change in a text editor (use search to find the current setting).

Define the extension directory:

extension_dir = “C:\php\ext”

Enable extensions. This will depend on the libraries you want to use, but the following extensions should be suitable for the majority of applications (remove the semi-colon comment):

extension=php_curl.dll
extension=php_gd2.dll
extension=php_mbstring.dll
extension=php_mysql.dll
extension=php_mysqli.dll
extension=php_pdo.dll
extension=php_pdo_mysql.dll
extension=php_xmlrpc.dll

If you want to send emails using the PHP mail() function, enter the details of an SMTP server (your ISP’s server should be suitable):

[mail function]
; For Win32 only.
SMTP = mail.myisp.com
smtp_port = 25
; For Win32 only.
sendmail_from = my@emailaddress.com

Step 4: Add C:\php to the path environment variable
To ensure Windows can find PHP, you need to change the path environment variable. From the Control Panel, choose System, (then “Advanced system settings” in Vista), select the “Advanced” tab, and click the “Environment Variables” button.

Scroll down the System variables list and click on “Path” followed by the “Edit” button. Enter “;C:\php” to the end of the Variable value line (remember the semi-colon). Now OK your way out. You might need to reboot at this stage.

Step 5: Configure PHP as an Apache module
Ensure Apache is not running (use “net stop Apache2.2″ from the command line) and open its \conf\httpd.conf configuration file in an editor. The following lines should be changed:
Line 239, add index.php as a default file name:

DirectoryIndex index.php index.html

At the bottom of the file, add the following lines (change the PHP file locations if necessary):

# PHP5 module
LoadModule php5_module “c:/php/php5apache2_2.dll”
AddType application/x-httpd-php .php
PHPIniDir “C:/php”

Save the configuration file and test it from the command line (Start > Run > cmd):

cd \Apache2\bin
httpd -t

Step 6: Test a PHP file
Create a file named index.php in Apache’s web page root (either htdocs or D:\WebPages) and add this code:

<?php phpinfo(); ?>

Ensure Apache has started successfully, open a web browser and enter the address http://localhost/. If all goes well, a “PHP version” page should appear showing all the configuration settings.