Font colour based on background colour

Very simple little php function that returns a black or white colour depending on the darkness of the given html colour.

function fontColour($colour){
	$r = hexdec($colour[0].$colour[1]);
	$g = hexdec($colour[2].$colour[3]);
	$b = hexdec($colour[4].$colour[5]);
	$sum = $r+$g+$b;
	if($sum>390){ return '000000'; }else{ return 'FFFFFF'; }
}

as i said, simple
enter a 6 char html background colour and it returns 000000 or FFFFFF for your text.