Mine cookies eller sessions fjernes ved dette script

Og det er et problem da jeg bliver logget ud før jeg har uploadet.

> Scriptet
<?php
$extlimit = "ja";
$limitedext = array(".jpg",".jpeg");
$sizelimit = "ja";
$sizebytes = "15000";
$sti = "/home/nicocarlos/public_html/testing/";
$absolute_path = $sti."profilbillede";
$id= "$yourstats3[ID]";


if($submit=="Upload"){
  $dir = "dir";
if ($file != "") {
  $ext=strrchr($file_name,'.');
  $ext=strtolower($ext);

if (file_exists($absolute_path."/".$id."".$ext)) {
  die("The picture allready exsist");
}

if (($sizelimit == "ja") && ($file_size > $sizebytes)) {
  die("The picture is too large. Maximum =  15 kb.");
}


if (($extlimit == "ja") && (!in_array($ext,$limitedext))) {
  die("Wrong filetype, only jpg and jpeg is avalible atm");
}

copy($file, $absolute_path."/".$id."".$ext) or die("The file couldn't be copyed to the server ".$absolute_path."/".$id."".$ext);

    #-+ Read the source image
    $src_img = ImageCreateFromJPEG($absolute_path."/".$id."".$ext);

    #Vælg bredden
    $tn_w = "146.25";

    #Hent billedets bredde og højde
    $imginfo = getimagesize($absolute_path."/".$id."".$ext);
    $org_w= $imginfo[0];
    $org_h = $imginfo[1];

    #Beregn højden i forhold til bredden
    $tn_h = "100";
           
    #Sæt det nye billede
    $dst_img = imagecreatetruecolor($tn_w,$tn_h);
       
    #Ændre det!
    ImageCopyResized($dst_img, $src_img, 0, 0, 0, 0, $tn_w, $tn_h, $org_w, $org_h);
               
    #Gem det!
    ImageJPEG($dst_img, $absolute_path."/".$id."".$ext, "95");
   
    #slet "midlertidige" filer fra serveren.
    imagedestroy($dst_img);
} else {
  print "try again";
}
echo "<p />";
echo $file_name." was uploaded";
mysql_query("UPDATE v_gu SET avatar_url='".$id."".$ext."' WHERE userid='$yourstats3[ID]'");
}
?>

<form method=POST action="avatarupload.php" enctype=multipart/form-data>
<p>Choose a picture:<br>
<input type=file name=file size=30>
<p><button name=submit type=submit value=Upload>
Upload
</button>
</form>