    <?php
    error_reporting(-1);
    $creditSum = 40000;
    $comission = 1000;
    $payout    = 5000;
    $payment   = 0;
    for ($month = 1; $month <= 15; $month++) {
        $creditSum = $creditSum * 0.03 + $creditSum + $comission - $payout;
        $payment   = $month * $payout;
        echo "{$month} месяц спустя: долг равен  {$creditSum}, оплачено {$payment}.\n";
        if ($creditSum * 0.03 + $creditSum + $comission < 5000) {
            $month++;
            $payment   = $payment + ($creditSum * 0.03 + $creditSum + $comission);
            $creditSum = $creditSum - $creditSum;
            echo "{$month} месяц спустя: долг равен  {$creditSum}, оплачено {$payment}.\n";
     
            break;
        }
    }