<?php
$cash = 3300;
$summary = $cash;
$bills = array(
		100 => 23,
		500 => 5,
		1000 => 0,
		5000 => 77
		);
 
krsort($bills);	
echo "<pre>";
print_r($bills);
echo "</pre>";
$billSum = array();
	foreach ($bills as $key => $value){
		$billSum[$key] = $key*$value;
		}
		$amount = array_sum($billSum);
		echo "Доступно на данный момент: $amount <br>";
	    if ($cash > $amount) 
	    {
	       echo 'В банкомате недостаточно средств для выдачи денег<br>';
	    }
else { 
echo "Вам будет выдано: <br>";
foreach ($bills as $nominal => &$count)
{
 
	if ($value != 0)
	{ 
		$arg = floor($cash / $nominal);
		if ($arg > $count){
		$arg = $count;
		}		
		$sum = $arg * $nominal;
		$cash -= $sum;
		$count -= $arg;
		if ($arg != 0)	
		{
			echo "$arg купюр номиналом $nominal на сумму $sum <br>";
		}
		}
}
echo "Общая сумма: $summary<br>";
}
echo "<pre>";
print_r($bills);
echo "</pre>";