upload probleem

<?php
if(isset($_FILES['worksheet']))
{
if(is_uploaded_file($_FILES['worksheet']['tmp_name'])) 
	{
		$filename = $_FILES['worksheet']['name'];
		$extensie = substr($filename, -3);
		if (strtoupper($extensie) != "GGB" )
		{  
			$message = "Gelieve een Geogebra-worksheet te selecteren.";
			include("insturen.inc");
			exit();
		}
		else 
		{ 
			$store_pad = $_SERVER['DOCUMENT_ROOT']."/app_oef";
			$file = $_FILES['worksheet']['name'];
			move_uploaded_file($_FILES['worksheet']['tmp_name'], "$store_pad/$file") or die("ERROR : fout tijdens het uploaden");
			chmod("$store_pad/$file",777);
			$new= $naam.'.'.strtolower($extensie);
			rename("$store_pad/$file","$store_pad/$new");
		}
             $sql="INSERT INTO inzendingen (titel, beschrijving , auteur , datum , aard , worksheet , werkblad , include)
			VALUES ('$titel','$beschrijving','$loginName','$vandaag','$aard','$naam','$naam','$naam')";
			mysql_query($sql);
             header("Location: leden.php?page=verstuurd");
	}
else
{
	$message = "Gelieve een Geogebra-worksheet te selecteren(2).";
	include("insturen.inc");
	exit();
}
?>


//form
<form action="" method="post" enctype="multipart/form-data">
  <table width="700" border="0" cellspacing="0" cellpadding="0">
  <tr>
      <td class="style5" colspan="2"><strong>
	  <?php 
	  if(isset($message))
	  {
	  	echo $message; 
		}
		?></strong></td>
    </tr>
    <tr>
<td height="30" colspan="2" class="style5">Geogebra-worksheet</td>
      <td height="30"><input name="worksheet" type="file" class="style5" size="20" ></td>
  </table>

<?php
if(isset($_FILES['worksheet']))
{
if(is_uploaded_file($_FILES['worksheet']['tmp_name'])) 
	{
		$filename = $_FILES['worksheet']['name'];
		$extensie = substr($filename, -3);
		if (strtoupper($extensie) != "GGB" )
		{  
			$message = "Gelieve een Geogebra-worksheet te selecteren.";
			include("insturen.inc");
			exit();
		}
		else 
		{ 
			$store_pad = $_SERVER['DOCUMENT_ROOT']."/app_oef";
			$file = $_FILES['worksheet']['name'];
			move_uploaded_file($_FILES['worksheet']['tmp_name'], "$store_pad/$file") or die("ERROR : fout tijdens het uploaden");
			chmod("$store_pad/$file",777);
			$new= $naam.'.'.strtolower($extensie);
			rename("$store_pad/$file","$store_pad/$new");
		}
             $sql="INSERT INTO inzendingen (titel, beschrijving , auteur , datum , aard , worksheet , werkblad , include)
			VALUES ('$titel','$beschrijving','$loginName','$vandaag','$aard','$naam','$naam','$naam')";
			mysql_query($sql);
             header("Location: leden.php?page=verstuurd");
	}
else
{
	$message = "Gelieve een Geogebra-worksheet te selecteren(2).";
	include("insturen.inc");
	exit();
}
?>
 
 
//form
<form action="" method="post" enctype="multipart/form-data">
  <table width="700" border="0" cellspacing="0" cellpadding="0">
  <tr>
      <td class="style5" colspan="2"><strong>
	  <?php 
	  if(isset($message))
	  {
	  	echo $message; 
		}
		?></strong></td>
    </tr>
    <tr>
<td height="30" colspan="2" class="style5">Geogebra-worksheet</td>
      <td height="30"><input name="worksheet" type="file" class="style5" size="20" ></td>
  </table>