Liste déroulante dynamique

<table>
<tr>
	<td> Article:
		<select name="article"  id="article" onChange="getSousArticle();" >
			<option selected value="">----choisir l'article---</option>
			<?php 
				mysql_connect("localhost","root","") or die("impossible de se connecter au serveur");
				mysql_select_db("article")or die("base de donne inexistant");
				$requete = "select * from article;";
				$listeArticle=mysql_query($requete);
				while($row = mysql_fetch_array($listeArticle))
				{
				echo '<OPTION VALUE="'.$row['id_article'].'">'.$row['lib_article'];
				}
				
			 ?>
		</select>
	 <td valign="top">Sous article<div id='div_sous_article' style='display:inline'>
                              <select size="1"  id="sous_article" name="sous_article" option="option" value=" ";>
                              </select>
                          </div></td>
                     
</table>

	<script type="text/javascript">
		var http = createRequestObject();
		function createRequestObject(){
			var request_;
			var browser = navigator.appName;
			if(browser == "Microsoft Internet Explorer"){
				request_ = new ActiveXObject("Microsoft.XMLHTTP");
			}
			else{
				request_ = new XMLHttpRequest();
			}
			return request_;
		}
		function getSousArticle(){
			http.open('get', 'get_sous_articles.php?id_article='+ document.getElementById('article').value);
			http.onreadystatechange = handleInfo_SousArticle;
			http.send(null);
		}

		function handleInfo_SousArticle(){
			if(http.readyState == 1){
				document.getElementById('loading').innerHTML='<img src=../images/loading.gif>';
			}
			if(http.readyState == 4){
				var response = http.responseText;
				alert(response);
				document.getElementById('loading').innerHTML="";
				document.getElementById('sous_article').innerHTML = response;
			}
		}	
	</script>

<?php 
mysql_connect("localhost","root","") or die("impossible de se connecter au serveur");
mysql_select_db("article")or die("base de donne inexistant");
$requete = "select * from sous_article where id_article='".$_GET['id_article']."';";
$listeArticle=mysql_query($requete);
while($row = mysql_fetch_array($listeArticle))
{
echo '<OPTION VALUE="'.$row['id_sous_article'].'">'.$row['lib_sous_article'];
 }
?>