Video Uploads

I can upload just about everything with this script; but I don't understand why it says that the videos i try to upload are zero length. ------------------------------ THE FORM ------------------------------ <form method="post" name="info" enctype="multipart/form-data" id="x-form" action="add.php"> <input type="hidden" name="max_size" value="51200000"> <input type="file" name="form_data"> <input type="submit" name="submit" value="Add Video"></form> ------------------------------ THE SCRIPT ------------------------------ ini_set ('display_errors', '1'); ini_set ('error_reporting', E_ALL); if (empty($_POST['submit'])) { include ('addform.php'); } else { $path = '/home/mydir/public_html/news/videos/'.$_FILES['form_data']['name']; $url = 'http://www.mysite.com/news/videos/'; $_POST = array_merge($_POST, $_FILES); if (!empty($_FILES['form_data']['name'])) {

       if ($_FILES['form_data']['size'] == 0)
       {
           echo 'Problem: '.$_FILES['form_data']['name'].' is zero length';
       }

       if ($_FILES['form_data']['size'] > $_POST['max_size'])
       {
           echo 'Problem: '.$_FILES['form_data']['name'].' is over '.$_POST['max_size'].' bytes.';
       }

       if (!is_uploaded_file($_FILES['form_data']['tmp_name']))
       {
           echo $_FILES['form_data']['name'].' is not uploaded.';
       }

       move_uploaded_file($_FILES['form_data']['tmp_name'], $path);

} }