PHP ! Probleme de synthaxe

Bonjour,
ce code ne m'affiche rien. dans un formulaire precedent je selectionne $a = departement, $f= style de devis et $k = en kit ou clé en main.
je souhaiterai donc qu'en fonction des choix l'affichage differe. j'ai donc préparé ce code et ca bug :) .v mon tableau est vide, ma requete ne renvoie rien !! comme d'habitude je demande conseil !! merci de m'aider si vous le pouvez

declaration des variables ici


if (($a == 'null'))
	{

	if (($f == 'null'))
	{
		
	$start = ($page_courante * $entrees_par_page - $entrees_par_page);
	
	$sql_entree = "SELECT * FROM chalet_table  WHERE kit = '" . $k . "' ORDER BY '" . $a ."'  "; 
	$result_entree = mysql_query( $sql_entree) or die( "Erreur : " . mysql_error() );

	$sql = "SELECT * FROM chalet_table  WHERE kit = '" . $k . "' ORDER BY '" . $a ."' LIMIT $start, $entrees_par_page  "; 
	$result = mysql_query( $sql) or die( "Erreur : " . mysql_error() );
	$nb_entrees = mysql_num_rows($result_entree);
	$total_pages = ceil($nb_entrees/$entrees_par_page);
	}
else{

$start = ($page_courante * $entrees_par_page - $entrees_par_page);
	
	$sql_entree = "SELECT * FROM chalet_table  WHERE style = '" . $f . "' AND kit = '" . $k . "' ORDER BY '" . $a ."'  "; 
	$result_entree = mysql_query( $sql_entree) or die( "Erreur : " . mysql_error() ); 
	
	$sql = "SELECT * FROM chalet_table  WHERE style = '" . $f . "' AND kit = '" . $k . "' ORDER BY '" . $a ."' LIMIT $start, $entrees_par_page  "; 
	$result = mysql_query( $sql) or die( "Erreur : " . mysql_error() );
	$nb_entrees = mysql_num_rows($result_entree);
	$total_pages = ceil($nb_entrees/$entrees_par_page);
		}

	}
	
else // else a
{
if ( ($f == 'null'))
{	
$start = ($page_courante * $entrees_par_page - $entrees_par_page);
	
$sql_entree = "SELECT * FROM chalet_table  WHERE departement = '" . $a . "' AND kit = '" . $k . "' ORDER BY '" . $a ."'  ";
$result_entree = mysql_query( $sql_entree) or die( "Erreur : " . mysql_error() );

$sql = "SELECT * FROM chalet_table  WHERE departement = '" . $a . "' AND kit = '" . $k . "' ORDER BY '" . $a ."' LIMIT $start, $entrees_par_page "; 
$result = mysql_query( $sql) or die( "Erreur : " . mysql_error() );
$nb_entrees = mysql_num_rows($result_entree);
$total_pages = ceil($nb_entrees/$entrees_par_page);
}
else

{
$start = ($page_courante * $entrees_par_page - $entrees_par_page);
	
$sql_entree = "SELECT * FROM chalet_table  WHERE departement = '" . $f . "' AND kit = '" . $k . "' AND departement = '" . $a . "' ORDER BY '" . $a ."'  ";
$result_entree = mysql_query( $sql_entree) or die( "Erreur : " . mysql_error() );

$sql = "SELECT * FROM chalet_table  WHERE style = '" . $f . "' AND kit = '" . $k . "' AND departement = '" . $a . "' ORDER BY '" . $a ."' LIMIT $start, $entrees_par_page "; 
$result = mysql_query( $sql) or die( "Erreur : " . mysql_error() );
$nb_entrees = mysql_num_rows($result_entree);
$total_pages = ceil($nb_entrees/$entrees_par_page);
}

}

Merci