<?php

error_reporting(-1);

function Credit($credit, $pay, $percent, $tax, $payForBill) {
	$total = 0;
	$credit += $payForBill;
	for ($month = 1; $month < 30; $month ++){
		
		$credit = $credit * $percent + $tax;
		
		if ($credit < $pay) {
			$total += $credit;
			break;
		}
		else {
			$credit -= $pay;
			$total += $pay;
		}
	}
	return $total;
}

$creditSum = 39999;
$payout = 5000;
$homoCreditTotal = Credit($creditSum, $payout, 1.04, 500, 0);
$softbankTotal = Credit($creditSum, $payout, 1.03, 1000, 0);
$strawberryBankTotal = Credit($creditSum, $payout, 1.02, 0, 7777);

echo "homoCredit: {$homoCreditTotal}\n";
echo "softbank: {$softbankTotal}\n";
echo "strawberryBank: {$strawberryBankTotal}\n";