When upgrading PHP on IIS, it is important to backup your php folder in the c:\program files(x86)\ folder before you begin.
- When upgrading, make a folder with the new version in the c:\program files(x86) folder
Above, we have made a v5.5 folder
We then download the version we want and extract it using WinRAR into the appropriate folder
Copy the php.ini from your old version. You will need to verify any ext files such as wincache.dll and make sure the newest version of the dll is placed into the ext folder (see folder above). For wincache upgrade, see version 1.3.5 and download it from here. Also the exts you use must be for the php version you use.
Copy the dll files to the ext folder after extracting them.
Open the IIS Manager. Click on PHP Manager and change this on all of your websites to the latest version.
Test your website by stopping and restarting IIS. If you receive a 500 Internal server error, your exts are wrong OR you may be missing a Visual Studio 2012 dll.
How do you tell if your exts or other information is wrong? After installing PHP, changing the version and restarting IIS, navigate to the new PHP folder and double click on php-cgi.exe. This will call php to work. If you receive an error, correct the error and restart IIS until you receive no errors.
If you receive the error – MSVCR100.dll is missing, download the Visual C++ Redistributable for Visual Studio. Get both the 32 and 64 bit version.