revisa los espacios entre palabras:
Código PHP:
$sql = "SELECT * FROM tarifas, hoteles, habitacion, regimen WHERE cod_hotel = $cod_hotel ";
$sql.= "AND cod_habitacion = id_habitacion ";
$sql.= "AND cod_regimen = id_regimen ";
$sql.= "ORDER BY desc_habitacion";
echo $sql;
saludos
