php man page for filter_id

FILTER_ID(3)								 1							      FILTER_ID(3)

filter_id - Returns the filter ID belonging to a named filter

SYNOPSIS
       int filter_id (string  $filtername)

DESCRIPTION
PARAMETERS
	      o $filtername
		- Name of a filter to get.

RETURN VALUES
	ID of a filter on success or FALSE if filter doesn't exist.

SEE ALSO
       filter_list(3).

PHP Documentation Group 													      FILTER_ID(3)