<?php

error_reporting(-1);

$monthPercent = 1.03;
$servicePayment = 1000;
$monthlyPayment = 5000;
$totalPayment = 0;
$totalCredit = 40000;

for ( ; ; ) {
	if ($totalCredit <= $paymentAfterAll) {
		$totalPayment = $totalPayment + $totalCredit * $monthPercent + $servicePayment;
		echo "Выплачено, потрачено $totalPayment\n";
		break;
	}
	$paymentAfterAll = $monthlyPayment - ( ($totalCredit * $monthPercent) - $totalCredit + $servicePayment);
	$totalCredit -= $paymentAfterAll; 
	$totalPayment += $monthlyPayment;
	$month ++;
	echo "$month месяц спустя, осталось выплатить $totalCredit, потрачено $totalPayment \n";
}