add(string $hook, callback $function_to_add, integer $priority = self::PRIORITY_NEUTRAL, integer $accepted_args = self::ARGUMENT_NEUTRAL)
Registers a filtering function
The name of the element to be filtered or action to be triggered
The name of the function/method that is to be called.
Optional. Used to specify the order in which the functions associated with a particular action are executed (default=10, lower=earlier execution, and functions with the same priority are executed in the order in which they were added to the filter)
Optional. The number of arguments the function accept (default is the number provided).