<?php
error_reporting(-1);
function countMoney($creditSum, $initialFee, $percent, $comission, $payment, $payout)
{
    $creditSum = $creditSum + $initialFee;
    $percent   = $percent + 100;
    for ($i = 1; $i <= 20; $i++) {
        $creditSum = $creditSum * $percent / 100 + $comission - $payout;
        $payment = $i * $payout;
        if ($creditSum * $percent / 100 + $comission < 5000) {
            $payment = $payment + ($creditSum * $percent / 100 + $comission);
            break;
        }
    }
    return $payment;
}
//variables
$creditSum  = 1000;
$payout     = 5000;
$payment    = 0;
$homocredit = countMoney($creditSum, 0, 4, 500, $payment, $payout);
echo "HomoCredit: {$homocredit} рублей.\n";
$softbank   = countMoney($creditSum, 0, 3, 1000, $payment, $payout);
echo "SoftBank: {$softbank} рублей.\n";
$stawberrybank = countMoney($creditSum, 7777, 2, 0, $payment, $payout);
echo "StrawberryBank: {$stawberrybank} рублей.\n";
$benefit = min($homocredit, $softbank, $stawberrybank);
echo "Наивыгодный кредит - {$benefit}!";