<?php
error_reporting(-1);
mb_internal_encoding('utf-8');

function creditCount($creditBalance, $monthlyPayment, $percent, $servicePayment, $additionalPayment = 0){
	if ($additionalPayment>0) {
		$creditBalance += $additionalPayment;
	}
	$paymentTotal = 0; /* Сколько всего отдал банку анон */
	
	/* Посчитаем расходы 20 раз на 20 месяцев вперед */ 
	for ($month = 1; $month <= 20; $month++) { 
		$creditBalance = ( $creditBalance * $percent ) + $servicePayment; 
		$payment = min($creditBalance, 5000);
		$creditBalance -= $payment;
		$paymentTotal += $payment;
		
	      /* Если баланс отрицательный — хватит считать */
	      if ($creditBalance <= 0) {
	          break;
	      }
	}
	
	return  $paymentTotal;
	
};

$homecredit = creditCount(40000, 5000, 1.04, 500);
$softbank = creditCount(40000, 5000, 1.03, 1000);
$strawberry = creditCount(40000, 5000, 1.02, 0, 7777);

echo 'homecredit: ' . $homecredit . "\n";
echo 'softbank: ' . $softbank . "\n";
echo 'strawberry: ' . $strawberry . "\n";