NAME
	filter_mapping - filter a mapping over a function

SYNOPSIS
	mapping filter_mapping(mapping m,string fun,object o,mixed extra)

DESCRIPTION
	Filter_mapping calls the function fun with every value in the mapping
	m as argument. If the function returns zero that value will be
	excluded from the restulting mapping, otherwise it will be included.
	If the optional extra argument is present that is also sent to the
	function as a second argumet.

SEE ALSO
	map_mapping,map_array,filter_array