<?php
$form_flight_id = filter_input(INPUT_POST, "flight_id", FILTER_SANITIZE_STRING);
$form_nb_place = filter_input(INPUT_POST, "nb_place", FILTER_VALIDATE_INT);
<?php
$form_flight_id = filter_input(INPUT_POST, "flight_id", FILTER_SANITIZE_STRING);
$form_nb_place = filter_input(INPUT_POST, "nb_place", FILTER_VALIDATE_INT);