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For nearly as long as there has been a WordPress, themes have included a functions.php file. This file provides a lot of extra, for lack of a better word, “functionality” to your WordPress blog. And while so much else about WordPress has changed over the years, it is quite remarkable how little about the functions.php file has evolved.

This is particularly true in light of WordPress’ ability to create child themes. Child themes are separate themes which extend the functionality of their “parent” themes by overriding key theme files. A child theme may only have a style.css file, to refer back to the parent. Or it might include a single.php file, because in the case of this one theme, you want all the functionality of the parent, but you’d like single posts and pages handled differently.

The trouble is: while a template file can override it’s parent, the WP functions.php file just basically loads the namespace with a bunch of free-floating functions, usually prepended with the name of the theme. There isn’t any “overriding” a function in PHP; the only thing you can do is write another function with still another name or prefix. That’s not very efficient use of the namespace and a recipe for confusion.

Instead, what I decided to try was putting my entire list of functions inside a class. Call it ParentFunctions. Inside this class, I also included a self-named initialization function that would do the adding of filters and actions as necessary. Then, all I need to do is instatiate my object – and be sure to call the “global” in each file where its necessary – and I’ve got an extensible model from which to create child themes.

Let’s look at ParentFunctions:

Among the advantages, here, is that our namespace is much cleaner. So is our code: instead of having to trawl through a couple dozen prefix_function_name entries, I can get straight to function_name. But better still, if I want to modify how a function works in a child theme, that’s even easier:

Using classes in your WP functions.php file provides a cleaner, easier interface for extending your themes for whatever you need.

It’s one of those bad habits we find hard to break as WordPress enthusiasts: installing plugins and then forgetting about them. This is especially true when you’ve installed them through the WordPress admin panels and then deactivated them because you decided you didn’t like them.

Well, now I’m getting very close to done with the new theme for DFE and I’ve got to go through all these plugins to find out what I’m keeping and what I’m not. You have to be very careful that the plugins you’re using do not conflict with one another or with template functions, and this new template is also going to be introducing a number of new functions and plugins both.

Because I’ve found that it just makes more sense to keep some things as template functions. I’ve not really bothered to play around with template functions because I’ve always seen the template as a display-only set of code. Indeed it is, but if there is additional processing to be done on display that isn’t needed anywhere else, WordPress provides the function file to deal with this. It’s not entirely MVC, but then, what is? Perfect systems don’t always work in an imperfect world.

Like eliminating unused plugins, moving display-altering functions to the template is about making things more efficient. If WordPress forces your server to spend time it doesn’t need to reading plugin files you’re not using, you take a hit on your performance. If you have functions which only operate on the display level, but which are contained in plugins, then each time any admin page is run, the plugin has to be turned on despite the fact that it will never be used. We’d like to avoid this, if at all possible.

On the other hand, adding huge volumes of code to your functions.php file has a similar effect: every time the front-end of your website is launched, you bog your system down with code. So, you need to balance what you use in the functions.php file and what you use as a plugin very carefully and make sure you’re using the most efficient code possible.