Moteur de recherche PHP SQL

<?php
mysql_connect("localhost","root","");
	mysql_select_db("SPIP");
// Récupère la variable
if(isset($_POST['ville']) || isset($_POST['theme']) || isset($_POST['type']) || isset($_POST['nomcat']) || isset($_POST['noment']))
	{
		if($_POST['ville']!=NULL || $_POST['theme']!=NULL || $_POST['type']!=NULL || $_POST['nomcat']!=NULL || $_POST['nomcat']!=NULL)
	{
	$ville=_request('$ville');
	$nomcat=_request('nomcat');
	$theme=_request('theme');
	$type=_request('type');
	$noment=_request('noment');
// la requete mysql
$sql = mysql_query(
"SELECT 'nomser' FROM 'entreprise' , 'service' , 'categorie'
WHERE entreprise.noment LIKE %$noment%" . " OR entreprise.ville LIKE %$ville%" . " 
OR service.theme LIKE %$theme%". " OR service.type LIKE %$type%" . " 
OR categorie.nomcat LIKE %$nomcat%
GROUP BY 'nomser'") or die (mysql_error());
}}
// affichage du résultat
while(list($nomser)=mysql_fetch_array($sql)){
echo 'Resultat de la recherche: '.$nomservice.',  <br />';
}
?>