function num2word($num, $words){
	$num = $num % 100;
	if ($num > 19) {
		$num = $num % 10;
	}
	switch ($num) {
		case 1: {
			return($words[0]);
		}
		case 2: case 3: case 4: {
			return($words[1]);
		}
		default: {
			return($words[2]);
		}
	}
}
 
print num2word(50, array('год', 'года', 'лет'));