If you are planning to use MySQL and PHP together, you must first install MySQL before you install PHP. This is because when you install PHP, you will need to provide the path to your installation of MySQL so they can talk to each other. If you have already installed PHP, uninstall it and then reinstall it after you finish installing MySQL.
Go to PHP.net
Click on "Downloads"
Scroll past the "beta" section to the "Latest stable version of PHP". Look for the heading "Windows Binaries". There may be 2 versions, choose the one labeled "Installer". In this example, the title is: "PHP 4.3.2 installer [1,035Kb] - 29 May 2003".
Pick a mirror site for download and save the file to your hard drive. In this example, the file name is "php-4.3.2-installer.exe".
Double-click on the file to begin installation. You'll see this welcome screen. It warns us to stop the webserver before you install PHP. Do this now. Then click "Next".
Read the License Agreement and click "I Agree".
Here we choose which kind of installation to perform. "Standard" is fine. Click "Next".
Now we choose the PHP installation folder. The default directory is fine. Click "Next".
Here you enter the address of your SMTP server and the 'from' address for the mail function. If you don't know this information, you can leave it at default and edit it later by editing the PHP configuration file.
Here you choose which kind of webserver you are using. I will be using Apache for the example so that's why I have Apache selected. Choose the appropriate one for you. Click "Next".
Now we're ready to install PHP. Click on "Next".
In this example, PHP was not able to automatically configure Apache so I got this message. We'll have to do this manually later. Click "OK".
Installation is now complete. Click "OK".
Now we have to configure the webserver software to use PHP properly.