<?php

error_reporting(-1);

$credit = 40000;
$bankPercent = 1.03;
$comission = 1000;
$payment = 5000;
$paymentTotal = 0;
$month = 0;

while (($credit * $bankPercent) + $comission > $payment) {
	$month++;
	$credit = ($credit * $bankPercent) + $comission - $payment;
	$paymentTotal = $paymentTotal + $payment;
	echo "$month месяц спустя: долг = $credit рублей, всего выплачено $paymentTotal рублей \n";
}

$month++;
$paymentTotal = $paymentTotal + (($credit * $bankPercent) + $comission);
echo "Прошло $month месяцев, было выплачено $paymentTotal";