paad/action/action_facultad.php

<?
$information = [
    'GET' => [],
];
header('Content-Type: application/json charset=utf-8');
$ruta = "../";
require_once "../class/c_login.php";

// check if the session is started
if (!isset($_SESSION['user'])) {
    http_response_code(500);
    echo json_encode([
        'error' => 'No se ha iniciado sesión'
    ]);
    exit;
}

$user = unserialize($_SESSION['user']);
try {
    if ($_SERVER['REQUEST_METHOD'] === 'GET') {
        // check parameters
        array_walk($information['GET'], function ($value) {
            if (!array_key_exists($value, $_GET)) {
                http_response_code(400);
                echo json_encode(['error' => "$value is required"]);
                exit;
            }
        });
        $data = $db->query(<<<SQL
                SELECT facultad_nombre, facultad_id, clave_dependencia
                FROM facultad
                WHERE facultad_id = :facultad_id OR :facultad_id IS NULL
                SQL
            ,
            [':facultad_id' => $user->facultad['facultad_id']]
        );
        echo json_encode($data, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);
    } else {
        http_response_code(405);
        echo json_encode(['error' => 'method not allowed']);
        exit;
    }
} catch (PDOException $th) {
    http_response_code(500);
    echo json_encode([
        'error' => $th->getMessage(),
        'query' => $db->getLastQuery(),
    ], JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);
    exit;
} catch (Exception $th) {
    http_response_code(500);
    echo json_encode([
        'error' => $th->getMessage(),
    ], JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);
    exit;
}