<?php

function credit($commission, $percent, $creditSum, $payout){
	for ($i=0; $creditSum > 0; $i++) {
	$creditSum =($creditSum * $percent) + $commission;
	  if($creditSum< $payout){
  
  
 $payout = $creditSum;
	 $creditSum = $creditSum - $payout;
	 	
	 	break;
 
	 }elseif($creditSum >= $payout ){
 
	 	$creditSum = $creditSum -$payout;
 

			return;
 
		}
		
	}
	
	
}

$balance = credit(500,0.04,39999,5000);
	echo "$balance";