upload.php:
<?php
 error_reporting(E_ALL);

 $map = "./store/"; // Map waar alles geupload wordt

 function upload_file($fTmp, $fNew) {
  if(file_exists($fNew)) {
   return false;
  } else {
   copy($fTmp, $fNew);
   return true;
  }
 }

 if(IsSet($_POST['submit'])) {
  for($i = 0; $i < count($_FILES['bestand']['name']); $i++) {
   if(IsSet($_FILES['bestand']['name'][$i]) && is_uploaded_file($_FILES['bestand']['tmp_name'][$i])) {
    if(!upload_file($_FILES['bestand']['tmp_name'][$i], $map.$_FILES['bestand']['name'][$i])) {
     $error = true;
    }
   }
  }

  if(IsSet($error)) {
   echo "Mislukt!";
  } else {
   echo "Gelukt!";
  }
 } else {
  if(IsSet($_POST['aantal'])) {
   $aantal = $_POST['aantal'];
  } else {
   $aantal = 5;
  }

?>
<form action="" method="post">
<input type="text" name="aantal" value="<?php echo $aantal; ?>" size="1">&nbsp;<input type="submit" name="aantal_submit" value="Aantal bestanden">
</form>
<br><br>
<form action="" method="post" enctype="multipart/form-data">
<?php
  for($i = 0; $i < $aantal; $i++) {
?>
Bestand <?php echo $i + 1; ?>: <input type="file" name="bestand[<?php echo $i; ?>]"><br>
<?php
  }
?>
<input type="submit" name="submit" value="Uploaden">
</form>
<?php
 }
?>