To download the latest version of PHP is give in the PHP Download
The steps to install PHP on Windows / XP / Vista is as follows:
Navigate to the folder where the PHP executable .zip was downloaded to as shown in Diagram 1.
Create a sub-directory in drive ‘C’ named C:\php as shown in Diagram 2.
Extract all the files from the .zip file to C:\php as shown in Diagram 3.
The installation of PHP is complete.