<?php

error_reporting(-1);

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

while (($credit * $bankPercent) + $comisson > $payment) {
	$month++;
	$credit = ($credit * $bankPercent) + $comission - $payment;
	$paymentTotal = $paymentTotal + $payment; 
	echo "Прошло $month месяцев, было выплачено $paymentTotal\n";
	if (($credit * $bankPercent) + $comission < $payment) {
		$month++;
		$paymentTotal = $paymentTotal + $credit;
		echo "Кредит закрыт, прошло месяцев: $month , было выплачено $paymentTotal\n";
	}
}