Erreur: undefined Index

$nom_destinataire_im      	=	$_POST["nom_destinataire_im"];
$numero_registre 		=	$_POST["numero_registre"];
$date_1_im      		=	$_POST["date_1_im"];
$resultat="select * from repertoire_des_importations where id_importation!=0";
if($nom_destinataire_im!="")
	$resultat.=" where nom_destinataire_im = '".$nom_destinataire_im."'";
if($numero_registre!="")
	$resultat.=" where n_du_registre_de_commerce_du_destinataire_reel = '".$numero_registre."'";	
if($date_1_im!="")
	$resultat.=" where annee='".$date_1_im."'";
$resultat.=" order by id_importation asc";
//echo $resultat; die();

$requete	=	mysql_query($resultat);