Renommer physiquement un dossier en PHP

Bonjour,
J'ai un véritable problème pour renommer un dossier physiquement. Logiquement, çà marche, avec UPDATE, mais pas physiquement. Mon problème se situe dans la partie où j'ai mis mon code en gras, question de mieux situer ma difficulté. Pouvez-vous m'aider?

Voici mon code : j'ai une table appelée "dossier" dans laquelle il y a tous les champs que vous voyez là ci-dessous.

<?php

$id = $_POST['id'];
$actif = $_POST['actif'];
$sys_ins_date = $_POST['sys_ins_date'];
$sys_upd_date = $_POST['sys_upd_date'];
$sys_del_date = $_POST['sys_del_date'];
$sys_ins_user = $_POST['sys_ins_user'];
$sys_upd_user = $_POST['sys_upd_user'];
$numero = $_POST['numero'];
$libelle = $_POST['libelle'];
$new_libelle = $_POST['new_libelle'];
$id_agt = $_POST['id_agt'];
$nomfull_agt = $_POST['nomfull_agt'];
$id_entite = $_POST['id_entite'];
$code_org = $_POST['code_org'];
$code_div = $_POST['code_div'];
$service = $_POST['service'];
$niv_conf = $_POST['niv_conf'];
$priorite = $_POST['priorite'];
$id_agt_resp = $_POST['id_agt_resp'];
$nomfull_agt_resp = $_POST['nomfull_agt_resp'];
$code_org_resp = $_POST['code_org_resp'];
$code_div_resp = $_POST['code_div_resp'];
$service_resp = $_POST['service_resp'];
$id_agt_dest = $_POST['id_agt_dest'];
$nomfull_agt_dest = $_POST['nomfull_agt_dest'];
$code_org_dest = $_POST['code_org_dest'];
$code_div_dest = $_POST['code_div_dest'];
$service_dest = $_POST['service_dest'];
$type = $_POST['type'];
$categorie = $_POST['categorie'];
$genre = $_POST['genre'];
$resume = $_POST['resume'];
$traitement = $_POST['traitement'];
$recommandation = $_POST['recommandation'];
$dtdebut = $_POST['dtdebut'];
$dtstatut = $_POST['dtstatut'];
$dtmaj = $_POST['dtmaj'];

include('lisaApp/connexion.php');

$url = "archives/dossiers/";
$doc = $libelle;
$doc_modif = $url.$doc;
$doc2 = $new_libelle;
$doc_modif2 = $url.$doc2;

$sql = mysql_query('SELECT id,libelle FROM dossier WHERE id = "'.$id.'" AND libelle = "'.$libelle.'" ');
while($data = mysql_fetch_array($sql))
{
$old_libelle = $data['libelle'];
$doc_modif = $url.$doc;
}
if (!is_dir($doc_modif2)) rename($doc_modif, $doc_modif2);

$req = mysql_query('UPDATE dossier SET actif = "'.$actif.'", sys_ins_date = "'.$sys_ins_date.'", sys_upd_date = "'.$sys_upd_date.'", sys_del_date = "'.$sys_del_date.'", sys_ins_user = "'.$sys_ins_user.'", sys_upd_user = "'.$sys_upd_user.'", numero = "'.$numero.'", libelle = "'.$libelle.'", new_libelle = "'.$new_libelle.'", id_agt = "'.$id_agt.'", nomfull_agt = "'.$nomfull_agt.'", id_entite = "'.$id_entite.'", code_org = "'.$code_org.'", code_div = "'.$code_div.'", service = "'.$service.'", niv_conf = "'.$niv_conf.'", priorite = "'.$priorite.'", id_agt_resp = "'.$id_agt_resp.'", nomfull_agt_resp = "'.$nomfull_agt_resp.'", code_org_resp = "'.$code_org_resp.'", code_div_resp = "'.$code_div_resp.'", service_resp = "'.$service_resp.'", id_agt_dest = "'.$id_agt_dest.'", nomfull_agt_dest = "'.$nomfull_agt_dest.'", code_org_dest = "'.$code_org_dest.'", code_div_dest = "'.$code_div_dest.'", service_dest = "'.$service_dest.'", type = "'.$type.'", categorie = "'.$categorie.'", genre = "'.$genre.'", resume = "'.$resume.'", traitement = "'.$traitement.'", recommandation = "'.$recommandation.'", dtdebut = "'.$dtdebut.'", dtstatut = "'.$dtstatut.'", dtmaj = "'.$dtmaj.'" WHERE id = "'.$id.'" ');

if($req)
{
?>
<script language="javascript">
alert('Dossier modifié avec succès');
window.close();
if(window.opener && !window.opener.closed)
{
window.opener.location.reload();
}
</script>
<?php
}
else
{
?>
<script language="javascript">
alert('La modification a échoué');
window.close();
</script>
<?php
}
?>