<?php

error_reporting(-1);
mb_internal_encoding('utf-8');

function calcCredit($creditSum, $payout, $percent, $comissionPayment, $openPayment, $paymentTotal = 0) {
	$creditSum += $openPayment;
	for($month = 1; $creditSum > 0; $month ++) {
		$creditSum = ($creditSum * $percent) + $comissionPayment;
		if($creditSum < $payout) {
			$payout = $creditSum;
		}
		$creditSum -= $payout;
		$paymentTotal += $payout;
		}
	return $paymentTotal;
}

$homoCreditTotal = calcCredit(39999, 5000, 1.04, 500, 0);
$softBankTotal = calcCredit(39999, 5000, 1.03, 1000, 0);
$strawberryBankTotal = calcCredit(39999, 5000, 1.02, 0, 7777);

echo "homoCredit: {$homoCreditTotal} руб.\n";
echo "softBank: {$softBankTotal} руб.\n";
echo "strawberryBank: {$strawberryBankTotal} руб.\n";

 ?>