array_flip duplicate keys as arrays

I figured somebody else must have needed this, so there'd have to be a PHP function for it... But I'm not finding it when I rtfm... Given an array like this: $t9 = array('F' => 'FIND', 'D' => 'FIND', 'E' =>'FIND', 'H' => 'HELP', 'I' => 'HELP'); I'm looking for a built-in function that returns this: array('FIND' => array('F', 'D', 'E'), 'HELP'=>array('H', 'I')) Or maybe I'm the only goofball that needs this? Obviously I can write it with a loop. But is there some quick built-in function I'm missing? -- Like Music? http://l-i-e.com/artists.htm