Ever wondered how you can manipulate WordPress filters and actions that are defined inside a PHP class?

I did! I was working on a project recently that needed a plugin. The only problem was that the plugin was inserting some unnecessary cruft into the header of my theme. So, I figured I’d just use the remove_filter function WordPress provides… right?

Hold on a second! It’s not working!? But I put in the function name just how the codex explains it:

remove_filter('wp_head', 'the_crufty_function');

Why would it not work? Time to do some troubleshooting… So, I opened up the main plugin PHP file in my code editor and began to look around. What’s this? It’s a class! Hmm… But why should that make a difference?

It seems that WordPress requires a special reference to the function if it is defined inside a class. If you, the reader, are at all familiar with PHP classes then you probably know that you can usually access a class’s functions like this:

$the_class_initiator_variable->some_function();

So, lets give that a try:

remove_filter('wp_head', $the_crufty_class->the_crufty_function);

Still nothing… Oh boy… What do I do now? I guess we’ll try some Googling…

…Hmm…

…Not finding much…

Well… after much searching and trying different things I finally came upon this:

remove_filter('wp_head', array(&$the_crufty_class, 'the_crufty_function'));

It works! Wonderful!

You take the class initiator variable and the name of the function and put it in an array. Simple as that!

Note: No, that ampersand is not a typo! It sets up a reference to the original variable instead of copying it’s value. You’d be surprised how many people don’t know what the ampersand does in PHP. I didn’t know for the longest time.

Also, because the remove_filter and remove_action functions are so similar this method applies to both.

There you have it! Just a quick little tip regarding an issue that doesn’t seem to be very well documented. I’m sure some of the experts out there already know of this but, I didn’t. I’m willing to assume there are some people out there like me who are racking their brains over this very issue.

Hope it helps!