Introduce __return_null()

[johnbillion]

I've recently had some uses for __return_null().

[scribu]

Could you list those uses by any chance?

[johnbillion]

Replying to scribu:

Could you list those uses by any chance?

Sure. The transient API and the options API let you short-circuit values using the pre_transient_{transient} and pre_option_{option} filters. __return_null() allows a null short circuit value. __return_false() can't be used because the short circuits use === to check for false.

[nacin]

I doubt there's much of a use case for returning null but it's nice to have the consistent function.

[nacin]

In [19607]:

Add __return_null() to complement the existing true, false, zero, and empty array methods. props johnbillion, fixes #18845.

[nacin]

In [19608]:

Update since. see #18845.