<?php
function Controle($NumeroTrain)
{
  $while = 0;
  $ARRAY = str_split($NumeroTrain);
  $result = 0;
  $while = 0;
  $arraycount = count($ARRAY);

  $arrayget = 0;
  $array1 = 1;

  while ($arraycount != $while)
  {
    $while++;
    if ( $array1 & 1 )
    {
      $two = $ARRAY[$arrayget];
      $two = 2*$two;
      if ( $two >= 10)
      {
        $two = $two-9;
      }
      $result = $result+$two;
      echo "<br>REs : $result</br>";
    }
    else
    {
      $one = $ARRAY[$arrayget];
      $result = $result+$one;
      echo "<br>REs : $result</br>";
    }
    $arrayget++;
    $array1++;
  }
  $arraytotal = ceil($result/10)*10;
  $result = $arraytotal-$result;
  return $result;
}
$NumeroTrain = '51800843004';
$result = Controle($NumeroTrain);
echo $result;
?>