If you use Metapad, a compact text editor for Windows, you might find these file filters useful. Download it, then double-click to merge the file with your registry. Then when you go to open a file, many more text files will appear by default.
Metapad is a good program, actually. Certainly it's better than Notepad on its own.
Personally I really like Scite. My only gripes being that whilst it works with PHP it doesn’t recognised the extension by default, and tabs don’t work on the non-install version.
Edit Plus is my favourite - been using it for several years now and supports syntax colouring, filters, auto-completion (ability to be turned off) and many other functions for PHP, Perl, C, Javascript, HTML - I couldn’t live without it!
I like metapad because it’s small, fast and has a very low memory footprint, and works like a normal Windows app. But I do have Programmer’s Notepad for when I need syntax highlighting.