Update, n'update pas

<form method="post" action="ajouthoraire.php" enctype="multipart/form-data">
	<input type="hidden" value="<?php $idhoraire ;?>" name="idhoraire"/>
	<center><h4>Horaire Magasin :</h4></center>
				<?php
					include('connect.php');
					try{
					$cnx = new PDO(DSN, LOGIN, PASSWORD, $options);
					$sql = "SELECT * FROM horaire";
					$res = $cnx->query($sql);
					echo "<table><tr>\n<th><center>Jour</center></th>\n<th><center>Matin</center></th>\n<th><center>Aprem-midi</center></th></tr>";	
					while ($ligne = $res->fetch()){
					
					echo "<tr>\n<td><center>".$ligne['jour']."</center></td>\n<td><center>
					<input type='text' value='".$ligne['heuredebutmat']."' name='heuredebutmat'/>
					<input type='text' value='".$ligne['heurefinmat']."' name='heurefinmat'/></center>\n</td>\n<td><center>
					<input type='text' value='".$ligne['heuredebutap']."' name='heuredebutap'/> 
					<input type='text' value='".$ligne['heurefinap']."' name='heurefinap'/></center></td></tr>";}		
										echo "</table>";}
										catch(PDOException $e){
						die("Echec : ".$e->getMessage()); 
					}
				?><br /><br />
	<input type="submit" value="Enregistrer" /> <input type="reset" value="Effacer" /></p><br /><br /></form>


<?php
		include('connect.php');
		$heuredebutmat=$_POST['heuredebutmat'];	
		$heurefinmat=$_POST['heurefinmat'];	
		$heuredebutap=$_POST['heuredebutap'];	
		$heurefinap=$_POST['heurefinap'];	
		$idhoraire=$_POST['idhoraire'];
		
		if(($heuredebutmat != "" && $heurefinmat != "" && $heuredebutap != "" && $heurefinap != "")){
		try{	
		$cnx = new PDO(DSN, LOGIN, PASSWORD, $options);
		$sql = "UPDATE horaire SET heuredebutmat='$heuredebutmat', heurefinmat='$heurefinmat', 
		heuredebutap='$heuredebutap', heurefinap='$heurefinap' WHERE idhoraire='$idhoraire'";
		$cnx->exec($sql);
		$cnx=null;
		echo 'Enregistrement du(des) nouvel(aux) horaire(s)  effectués !<br />';}
		catch(PDOException $e){
		die("Echec : ".$e->getMessage()); }}			
		else{
			echo 'Erreur : Vous devez remplir tout les champs.';}
	?>