<?php

$bills = array(
	100 => 23,
	500 => 5,
	1000 => 0,
	5000 => 200);
	

	
for($z = 0; $z++; $z <= count($bills)) {
	if($bills[$z] == 0){
		unset($bills[$z]);
	}
}

echo $bills[2];