Canonical callback representation

[scribu]

Since PHP 5.3, you have various ways of passing the same callback:

add_filter( 'the_content', array( 'My_Plugin_Main_Class', 'the_content' ) );

add_filter( 'the_content', 'My_Plugin_Main_Class::the_content' );

add_filter( 'the_content', '\\My_Plugin_Main_Class::the_content' );

Currently, you have to use the exact same syntax in remove_action(), or it won't work.

It would be nice if _wp_filter_build_unique_id() converted all these variations to a canonical representation.

Sprung out of #23259

+1.

Another variant:

add_filter( 'the_content', ['Class_Name', 'static_callback_method'] );

But that should be equal to your first example.

It seems the string syntax was added even earlier:

// Type 4: Static class method call (As of PHP 5.2.3)
call_user_func('MyClass::myCallbackMethod');

From ​http://php.net/manual/en/language.types.callable.php

23265.diff​ fixes the most common case and has 23265.tests.diff​ to go with it.

I looked at the same-ish thing here #21267

Here was my patch:
​https://core.trac.wordpress.org/attachment/ticket/21267/filter-callback-keys.diff

Main problem is closures

Replying to toscho:

Another variant:

add_filter( 'the_content', ['Class_Name', 'static_callback_method'] );

But that should be equal to your first example.

Yep, that's just shorthand for an array in 5.4+.

With closures, they're pretty much going to have to be assigned to a variable to do anything with them. The only thing I can think of doing is involving where they were defined via ReflectionFunction, but that seems a little horrible.

In 24251:

Add a delimiter to _wp_filter_build_unique_id()'s handling of static method callbacks. props scribu, fixes #23265.

In 1294/tests:

Tests for canonical callback representation. props scribu, see #23265.