$sql="SELECT Id,Matricola,Nominativo,Sede,Telefono,Mail FROM Utenti WHERE Matricola = '".$MatrCall."' LIMIT $primo, $per_page";
$query_limit = mysql_query($sql) or die(mysql_error());

You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1