Undefined index: fichier

Je suis le undefined index erreur que je viens pour la première fois dans mon formulaire de chargement de la page ou si je passe à la page suivante et cliquez sur le bouton de retour, alors j'ai le même message d'erreur.
Si j'upload un fichier alors qu'il fonctionne très bien et le message d'erreur s'éloigne.

J'ai aussi essayé ceci:

global $file;
if (!isset($file)) {
    $file = '';
}

Voici mon code:

<form id="uploadForm" name="upload" enctype="multipart/form-data"/>
  <fieldset>
    <input type="hidden" name="MAX_FILE_SIZE" value="30000" />
    <input type="file" name="file" />
<?php
echo '<pre>';
var_dump($_REQUEST['file']);
echo '</pre>';

$uploaded = new upload;
//set Max Size
$uploaded->set_max_size(350000);
//Set Directory
$uploaded->set_directory("data");
//Set Temp Name for upload.
$uploaded->set_tmp_name($_FILES['file']['tmp_name']);
//Set file size
$uploaded->set_file_size($_FILES['file']['size']);
//set file type
$uploaded->set_file_type($_FILES['file']['type']);
//set file name
$uploaded->set_file_name($_FILES['file']['name']);
//start copy process
$uploaded->start_copy();
if($uploaded->is_ok()) 
    echo " upload is doen.";
else
    $uploaded->error()."<br>";
?>
    <div class="filesize">JPG minimaal 800x60 pixels max. 2Mb</div>
    <a href="" class="submit" title="Upload your own phooto"><span> Upload your own photo </span></a>

upload_inc.php

<?
class upload
{
var $directory_name;
var $max_filesize;
var $error;
var $user_tmp_name;
var $user_file_name;
var $user_file_size;
var $user_file_type;
var $user_full_name;
function set_directory($dir_name =".")
{
$this->directory_name = $dir_name;
}
function set_max_size($max_file = 2000000)
{
$this->max_filesize = $max_file;
}
function error()
{
return $this->error;
}
function is_ok()
{
if(isset($this->error))
return FALSE;
else
return TRUE;
}
function set_tmp_name($temp_name)
{
$this->user_tmp_name = $temp_name;
}
function set_file_size($file_size)
{
$this->user_file_size = $file_size;
}
function set_file_type($file_type)
{
$this->user_file_type = $file_type;
}
function set_file_name($file)
{
$this->user_file_name = $file;
$this->user_full_name = $this->directory_name."/".$this->user_file_name;
}
function start_copy()
{
if(!isset($this->user_file_name))
$this->error = "You must define filename!";
if ($this->user_file_size <= 0)
$this->error = 'File size error (0):' . $this->user_file_size . 'KB <br>';
if ($this->user_file_size > $this->max_filesize)
$this->error = 'File size error (1):' . $this->user_file_size . 'KB<br>';
if($this->user_file_type != "image/jpeg")
$this->error = "the image must be jpeg extension";
if (!isset($this->error))
{
$filename = basename($this->user_file_name);
if (!empty($this->directory_name))
$destination = $this->user_full_name;
else
$destination = $filename;
if(!is_uploaded_file($this->user_tmp_name))
$this->error = "File " . $this->user_tmp_name . " is not uploaded correctly.";
if (!move_uploaded_file ($this->user_tmp_name,$destination))
$this->error = "Impossible to copy " . $this->user_file_name . " from your folder to destination directory.";
}
}
}
?>