<?php

error_reporting(-1);

function totalPayment($creditSum, $percent, $monthlyPayment, $servicePayment, $newAccPayment) {
    $paymentTotal = 0; 
    $creditSum += $newAccPayment;
    while ($creditSum > 0) {
        $creditSum = ($creditSum * $percent) + $servicePayment;
        if ($creditSum < $monthlyPayment) {
            $monthlyPayment = $creditSum; 
        }       
        $creditSum -= $monthlyPayment;	
        $paymentTotal = $paymentTotal + $monthlyPayment;
    }
    return $paymentTotal;
}

$creditSum = 39999;
$monthlyPayment = 5000;
$homoCredit = totalPayment($creditSum, 1.04, $monthlyPayment, 500, 0);
$softBank = totalPayment($creditSum, 1.03, $monthlyPayment, 1000, 0);
$strawberryBank = totalPayment($creditSum, 1.02, $monthlyPayment, 0, 7777);
echo "homoCredit: {$homoCredit} roubles.\n";
echo "softBank: {$softBank} roubles.\n";
echo "strawberryBank: {$strawberryBank} roubles.\n";