Recently while trying to find the PHP file that I needed to edit, I was once again frustrated by Windows seeming inability to search the text contained in PHP files 
Windows obviously has the capability to do file content searches since it does so for .txt files.
Finally I got fed up with it and decided to find out how to enable full text searching of .php documents. Here is what worked for me, I hope you will find it helpful too 
How to index file contents for any extension (including PHP files)
- Open the Windows Start menu and type in the search box: “Change How Windows Searches”, choose the Control Panel option that matches your search
- Choose the “Advanced” button (it will likely have a shield icon on it)
- Choose the “File Types” tab in the Advanced Options window.
- Scroll down to find the extension that you want Windows to index file contents of
- If your extension is not listed, enter the correct extension… for example “.php” into the input box and press the Add button.
- Once the appropriate extension is highlighted, change the indexing property to “Index Properties and File Contents” and choose OK
- Voila, Windows should now be able to search the file contents for the extension that you added!
