<?php

error_reporting (-1);

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

for ( $month = 1; $month <= 20; $month++ ) {
	
	$creditBalance = ($creditBalance * $percent) + $servicePayment;
	$creditBalance = $creditBalance - $monthlyPayment ;
	$paymentTotal = $paymentTotal + $monthlyPayment;
	echo "{$month} месяц спустя: долг = {$creditBalance}руб, выплачено всего {$paymentTotal}\n";
	
	if  ( $creditBalance < $monthlyPayment ) {
		$monthlyPayment = $creditBalance;
	echo "{$paymentTotal}";
	}
	 
}