<?php

function creditsTotal($bankName, $creditSumm, $payment, $percent, $commission){


    for($month = 0, $totalPayment = 0; $creditSumm >0; $month++){
        if ((($creditSumm * $percent) + $commission) <= $payment)
        {
            $payment = (($creditSumm * $percent) + $commission);
        }
        $creditSumm = (($creditSumm * $percent) + $commission) - $payment;
        $totalPayment += $payment;
    }
    return array(
        'month' => $month,
        'bankName' => $bankName,
        'totalPayment' => round($totalPayment, 1)
    );
}

$homobank = creditsTotal('Homobank', 39999, 5000, 1.04, 500);
$softbank = creditsTotal('Softbank', 39999, 5000, 1.03, 1000);
$strawberryBank = creditsTotal('StrawberryBank', 39999+7777, 5000, 1.02, 0);


echo "{$homobank['bankName']}: будет заплачено {$homobank['totalPayment']} за {$homobank['month']} месяцев\n";
echo "{$softbank['bankName']}: будет заплачено {$softbank['totalPayment']} за {$softbank['month']} месяцев\n";
echo "{$strawberryBank['bankName']}: будет заплачено {$strawberryBank['totalPayment']} за {$strawberryBank['month']} месяцев\n";