Does this code contain any useless parts? Im am using it for a fast JSON API without routes. Is the class loader efficient enough? Are there any better options? Is ReflectionMethod slow if used once?

<?php

/*
 * Init stuff
 */

session_start();
define('ROOT', realpath(dirname(__FILE__)) . '/');
set_include_path(ROOT . 'src/');
spl_autoload_extensions('.php');
spl_autoload_register();
ini_set('error_reporting', E_ALL & ~E_DEPRECATED);
ini_set('display_errors', 1); //To change in prod to 0 <<<<<<<<<<<<<<<<<<<<<<<<<
ini_set('log_errors', 1);
ini_set('error_log', ROOT . 'tmp/logs/application.log');
date_default_timezone_set('Europe/Paris');

/*
 * Process stuff
 */

$params = explode('/', trim(key($_GET), '/'));
$paramsCount = count($params);
if ($paramsCount >= 2) {
  try {
    $controllerMethod = new ReflectionMethod('\app\controller\\' . $params[1], $params[2]);
    if ($paramsCount - 2 >= $controllerMethod->getNumberOfRequiredParameters()) {
      \ens\controller\Request::$lang =& $params[0];
      \ens\controller\Request::$data =& $_POST;
      $response = $controllerMethod->invokeArgs(null, array_splice($params, 3));
    } else {
      $response = array('status' => 400);
    }
  } catch (ReflectionException $e) {
    $response = array('status' => 300);
  }
} else {
  $response = array('status' => 301);
}
if (!headers_sent()) {
  header('Content-Type: application/json');
}
echo json_encode($response);