We bloggers have it rough. We live in a world full of more WordPress themes than you can shake a stick at, yet most of us are still tied to one old, worn out template. It’s unfortunate, but let’s be honest here—changing themes is a huge ordeal.
Generally speaking, whenever you opt for a new theme, you’re going to have to do a fair amount of customization to get everything just right for your site. By the time you get to your third or fourth theme, you’ll probably begin to grow a little weary of reinventing the wheel with each new design.
Fortunately, savvy users like you can solve this problem by creating a user-defined functions file that will work with any WordPress theme. The idea here is to place all of your common, customized design elements—like an author bio or a sales widget for your sidebar, for instance—within functions that reside in a separate, non-theme file. This serves a twofold purpose: