PHP: Une simple API GET/POST

voici un exemple de simple code

<?php
header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8");
header("Access-Control-Allow-Methods: GET, POST, PATCH, PUT, DELETE, OPTIONS");
header("Access-Control-Max-Age: 3600");
header("Access-Control-Allow-Headers: Content-Type, Access-Control-Allow-Headers, Authorization, X-Requested-With");

$method = $_SERVER['REQUEST_METHOD'];

switch ($method) {
    case 'GET':
        handleGetRequest();
        break;
    case 'POST':
        handlePostRequest();
        break;
    default:
        handleInvalidRequest();
        break;
}

function handleGetRequest() {
    echo json_encode(array("message" => "Handling GET request."));
}

function handlePostRequest() {
    $data = json_decode(file_get_contents("php://input"));
    echo json_encode(array("message" => "Handling POST request.", "data" => $data));
}

function handleInvalidRequest() {
    http_response_code(405);
    echo json_encode(array("message" => "Invalid request method."));
}