Helper Methods for Filters

WordPress offers some helper methods for filters. If you want to pass true or false to a filter, you can use:

add_filter('my_filter', '__return_true'); 
add_filter('my_filter', '__return_false'); 

Other available filter helper methods are:

add_filter('my_filter', '__return_empty_array'); 
add_filter('my_filter', '__return_zero'); 
add_filter('my_filter', '__return_null'); 
add_filter('my_filter', '__return_empty_string');