Flight is designed to be an extensible framework. The framework comes with a set of default methods and components, but it allows you to map your own methods, register your own classes, or even override existing classes and methods.

If you are looking for a DIC (Dependency Injection Container), hop over to the Dependency Injection Container page.

Mapping Methods

To map your own simple custom method, you use the map function:

// Map your method
Flight::map('hello', function (string $name) {
  echo "hello $name!";

// Call your custom method

This is used more when you need to pass variables into your method to get an expected value. Using the register() method like below is more for passing in configuration and then calling your pre-configured class.

Registering Classes

To register your own class and configure it, you use the register function:

// Register your class
Flight::register('user', User::class);

// Get an instance of your class
$user = Flight::user();

The register method also allows you to pass along parameters to your class constructor. So when you load your custom class, it will come pre-initialized. You can define the constructor parameters by passing in an additional array. Here's an example of loading a database connection:

// Register class with constructor parameters
Flight::register('db', PDO::class, ['mysql:host=localhost;dbname=test', 'user', 'pass']);

// Get an instance of your class
// This will create an object with the defined parameters
// new PDO('mysql:host=localhost;dbname=test','user','pass');
$db = Flight::db();

// and if you needed it later in your code, you just call the same method again
class SomeController {
  public function __construct() {
    $this->db = Flight::db();

If you pass in an additional callback parameter, it will be executed immediately after class construction. This allows you to perform any set up procedures for your new object. The callback function takes one parameter, an instance of the new object.

// The callback will be passed the object that was constructed
  ['mysql:host=localhost;dbname=test', 'user', 'pass'],
  function (PDO $db) {

By default, every time you load your class you will get a shared instance. To get a new instance of a class, simply pass in false as a parameter:

// Shared instance of the class
$shared = Flight::db();

// New instance of the class
$new = Flight::db(false);

Keep in mind that mapped methods have precedence over registered classes. If you declare both using the same name, only the mapped method will be invoked.

Overriding Framework Methods

Flight allows you to override its default functionality to suit your own needs, without having to modify any code.

For example, when Flight cannot match a URL to a route, it invokes the notFound method which sends a generic HTTP 404 response. You can override this behavior by using the map method:

Flight::map('notFound', function() {
  // Display custom 404 page
  include 'errors/404.html';

Flight also allows you to replace core components of the framework. For example you can replace the default Router class with your own custom class:

// Register your custom class
Flight::register('router', MyRouter::class);

// When Flight loads the Router instance, it will load your class
$myrouter = Flight::router();

Framework methods like map and register however cannot be overridden. You will get an error if you try to do so.