remove_action: Initial attempt failed while a later attempt worked

Question

I hope this is the right place to post this - if not, please just simply direct me to the right place!

I recently came across a plugin that, among other things, added a meta entry to the header. I needed to remove this action. The add_action entry looked like this:

add_action( 'wp_head', array( &$this, 'addMetaData' ) );

"this" is in relation to the class, called Vc_Base.

My initial reaction was to add the following to my functions.php:

function removeAddMetaData() {
    $vc = new Vc_Base();
    remove_action('wp_head', array(&$vc, 'addMetaData'),10000);
}
add_action('init', 'removeAddMetaData', 10000);

This did not work. I also tried changing 10000 to other values.

What DID end up working was this:

function removeAddMetaData() {
    remove_action('wp_head', array(visual_composer(), 'addMetaData'));
}
add_action('init', 'removeAddMetaData');

I tracked down visual_composer() and it only has one line:

return vc_manager()->vc();

I tracked down vc_manager()->vc() and, among a few other things, it contains these lines:

$vc = new Vc_Base();
$this->factory['vc'] = $vc;
return $this->factory['vc'];

So, if that's just doing what I did (in a round-about way), why didn't my initial idea work? I'd really appreciate some feedback since I feel I'll understand WordPress/PHP a whole lot more if I can understand this!

Thanks in advance.

Answer 1

Your first method doesn't work because you create a new instance of the class and try to remove the action from that new instance. That new instance you created is not the same instance that the action was added to, so it doesn't work.

In the second example, you get the original instance that was created by the plugin, so removing the action from that instance succeeds.

Have a look at this question for some other ways classes may instantiate themselves in plugins.