ho realizzato l'upload in php utilizzando la barra di scorrimento aiutandomi con jquery...ma effettua l'inserimento,ma la variabile file quando la passo e la stampo..mi restituisce null

codice:
<head>
<link href="/uploadify/uploadify.css" type="text/css" rel="stylesheet" />
<script type="text/javascript" src="/uploadify/jquery-1.4.2.min.js"></script>
<script type="text/javascript" src="/uploadify/swfobject.js"></script>
<script type="text/javascript" src="/uploadify/jquery.uploadify.v2.1.4.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
$('#file').uploadify({
'uploader'  : '/uploadify/uploadify.swf',
'script'    : '/uploadify/uploadify.php',
'cancelImg' : '/uploadify/cancel.png',
'folder'    : '/uploadify/materiale',
'displayData' : 'percentage',
'displayData' : 'speed',
'auto'      : true
});
});
</script>
<title>..:: Download file ::..</title>
</head>
<body bgcolor="#FFFFFF">
<?
include "header.php";
require "inc/settings.php";
?>
<div class="container">
	<div class="content">
		<div class="content-wrapper">
			<div class="smallright">
				<div id="form_inserimento" style="display:none;">
        				<form action="materiale_inserisci.php" class="insert" name="frm_corsi" id="frm_corsi" method="post" enctype="multipart/form-data">
						<fieldset>
						<h4>aggiungi file</h4>
						<div class="item">
                			<label for="titolo">titolo *</label>
                    		<input type="text" class="input w300" name="titolo" />
						</div>
						<div class="item">
                			<label for="file">file *</label>
                    		<input type="file" class="input w300" name="file" id="file"/>
						</div>
							</fieldset>
						<div class="form-submit">
							<input type="submit" name="inserisci" value="inserisci" />
							<input type="button" value="annulla" onClick="$('#form_inserimento').hide();" />
						</div>
							</form>
            				

            		</div>
					<table class="view"> 
            		<col />
               	 	<col width="40" />
                	<col width="40" />
					<caption>			 
            		<span class="label">lista file associati</span>
					<span class="action add">
					aggiungi file
					</span>
            		</caption>
					<thead>
					<tr>
					<th>Titolo</th>
					<th> </th>
            		<th> </th>
					</tr>
					</thead>
					<tbody>
					<?
		$query ="SELECT * FROM materiale ORDER BY titolo";
		$result = mysql_query($query) or die(mysql_error());
		if (mysql_num_rows($result) > 0) 
		{
			while ($file = mysql_fetch_assoc($result)) 
			{
			?>
			<tr>
            <td>" target="_blank"><?=$file["titolo"]?></td>
<td class="icon">">[img]img/icons/delete.png[/img]</td>
			<td class="icon">" target="_blank">[img]img/icons/view.png[/img]</td>            
			</tr>
			<?
			}
		} 
		else 
		{
			?>
			<tr><td colspan="3">nessun file associato</td></tr>
			<?
		}
			?>
			</tbody>
			</table>
				</div>
			</div>
		<br class="clear" />		
	</div>
</div>    
</body>
fin qui tutto ok...
ma qnd passo la variabile file nel file:materiale_inserisci.php
codice:
<?
require "inc/settings.php";
$titolo = $_POST["titolo"];
$files = $_FILES["file"]["name"];
echo $files;
$cartella = $_SERVER["DOCUMENT_ROOT"].CARTELLA_SOFTWARE."/materiale/";
//if(is_uploaded_file($_FILES["file"]["tmp_name"])) 
//{
//	move_uploaded_file($_FILES["file"]["tmp_name"], $cartella.$_FILES["file"]["name"]) or die ("Impossibile spostare il file, controlla l'esistenza o i permessi della directory dove fare l'upload.");
//}
$query = "INSERT INTO materiale (titolo, file) VALUES ('".$titolo."','".$_FILES["file"]["name"]."')";
mysql_query($query) or die(mysql_error());
//header("location:materiale.php");
?>