<?php

error_reporting(-1);

$creditBalance  = 40000;
$percent        = 1.03;
$servicePayment = 1000;
$monthlyPayment = 5000;
$paymentTotal   = 0;
$debt = 0;

for ($month = 1; $month <= 20; $month++) {
        $creditBalance = $creditBalance * $percent + $servicePayment;
    	$debt = $creditBalance;
	if ($debt > 1000) {
	    $creditBalance = $debt - $monthlyPayment;
		$paymentTotal  = $paymentTotal + $monthlyPayment;
		echo "{$month} месяц спустя: долг = {$debt} руб, выплачено всего {$paymentTotal} руб. \n";
	} else {
        echo "Осталось выплатить всего {$debt} и кредит погашен.\n";
        break;
    }
}