<?php
error_reporting(-1);
$amount=6600;
$bills = array( 100 => 0,
				200 => 3,
				500 => 1,
				1000 => 0,
				2000 => 4,
				5000 => 1
	);
echo "Сумма: $amount \n";
if ($amount%100 !=0) 
	echo "Выдача невозможна: сумма не кратна 100";
else{
	$finalstr="Выдача возможна, число купюр: ";
	$rbills=array_reverse($bills, true);
	foreach ($rbills as $key => $value){
		$result=floor($amount/$key);
		$bonds=min($result,$value);
		$amount=$amount-($bonds*$key);
		$finalstr.="$bonds"."x$key ";
		if ($amount==0) $success=true;
	}
	if($success) echo $finalstr;
	else echo "Выдача невозможна: не хватает купюр.";
}

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