Update: I’ve revised the directions slightly to show the difference between 10.3 & 10.4, plus I’ve added a screen shot.
Just a quick note to document how to change which applications are used to open specific file types.
All you have to do, is select a file in the Finder and ‘Get Information’ (cmd + i or right-click > Get Info or cmd + click > Get Info) for it. Then toggle the ‘Open with…’ option and choose the proper application.
To make sure that every file of that type (every php file for example) uses the new application, make sure you choose that option below the application drop down box (it may be grayed out until you’ve chosen an alternate application from the current default:
10.3: “The generic application for documents of this type”
10.4: “Use this application to open all documents like this.” > Click the Change All button.