[wp-hackers] anonymous functions for do_action and apply_filters

scribu mail at scribu.net
Mon Dec 20 20:59:29 UTC 2010

> add_filter('the_title', function($title) { return '<b>'. $title. '</b>';
> });

Yes, this is already possbile in WP 3.0:


On Mon, Dec 20, 2010 at 10:49 PM, Nathaniel Taintor <
goldenapplesdesign at gmail.com> wrote:

> I think its generally frowned upon, because if you add an anonymous
> function, then you have no way of removing it, other than calling
> remove_all_filters.

A valid concern; discretion is advised.

There are also concerns about memory leaks caused by using lambda functions
> in php. The add_filter code you cited would create a new function every
> time
> it was called, which may not be a big deal in your case (you're not likely
> to trigger the title filter more than 20-50 times in any one page), but
> would still be slightly less efficient than defining the function once.

That's a common misconception. PHP will evaluate it only once. It will
internally create separate instances of Closure objects if there is a 'use'

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