api.php

<?php
require "bootstrap.php";

// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Origin
header("Access-Control-Allow-Origin: *");

header("Content-Type: application/json; charset=UTF-8");

// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Methods
header("Access-Control-Allow-Methods: GET,POST,PUT,DELETE");

header("Access-Control-Max-Age: 3600"); // Maximum number of seconds the results can be cached.

// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Headers
header("Access-Control-Allow-Headers: Content-Type, Access-Control-Allow-Headers, Authorization, X-Requested-With");

function getRoute($url){

    $url = trim($url, '/');
    $urlSegments = explode('/', $url);

    $scheme = ['controller', 'params'];
    $route = [];

    foreach ($urlSegments as $index => $segment){
        if ($scheme[$index] == 'params'){
            $route['params'] = array_slice($urlSegments, $index);
            break;
        } else {
            $route[$scheme[$index]] = $segment;
        }
    }

    return $route;
}

// $uri = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
$uri = parse_url($_SERVER['REQUEST_URI'], PHP_URL_QUERY);
$route = getRoute($uri);

$requestMethod = $_SERVER["REQUEST_METHOD"];

$controllerName = $route['controller'];

switch($controllerName) {
    case 'users' :
        // GET api.php?/users
        // POST api.php?/users
        $controller = new UsersController($requestMethod);
        break;
    default :
        header("HTTP/1.1 404 Not Found");
        exit();
}

$controller->processRequest();