The callback functions attached to filter hook $tag are invoked by calling this function. This function can be used to create a new filter hook by simply calling this function with the name of the new hook specified using the $tag parameter.
The function allows for additional arguments to be added and passed to hooks.
function example_hook($string, $arg1, $arg2)
{
//Do stuff
return $string;
}
$value = apply_filters('example_filter', 'filter me', 'arg1', 'arg2');