Structure of a Laravel application

Whether you are a beginner in PHP or an experienced developer in a different language, it might not always be obvious how an HTTP request reaches a Laravel application. Indeed, the request lifecycle is fundamentally different from plain PHP scripts that are accessed directly by their URI (for example, GET http://example.com/about-us.php).

The public/ directory is meant to act as the document root; in other words, the directory in which your web server starts looking after every incoming request. Once URL rewriting is properly set up, every request that does not match an existing file or directory hits the /public/index.php file. This file includes the Composer autoloader file, which loads in dependencies (including the Laravel framework components) and also where to look for your application's code. Your application is then bootstrapped, loading configuration variables based on the environment. Once this is done, it instantiates a new service container instance, which in turn handles the incoming request, uses the HTTP method and URL used to access the application (such as POST /comments), and passes the request off to the correct controller action or route for handling.

In this chapter, we are only covering the general mechanisms of how Laravel works, without looking at the detailed implementation examples. For the majority of developers, who just want to get the job done, this is sufficient. Moreover, it is much easier to delve into the source code of Laravel once you have already built a few applications. Nevertheless, here are some answers to the questions that might crop up when exceptions are thrown or when you navigate through the source code. In doing so, you will come across some methods that are not documented in the official guide, and you might even be inspired to write better code.

Browsing the API (http://laravel.com/api) can be somewhat intimidating at first. But it is often the best way to understand how a particular method works under the hood. Here are a few tips:

Laravel 5 started life as Laravel 4.3, but was promoted to its own major version when it became apparent that this new version was going to be a radical departure from version 4 of the framework. Laravel 5 builds on Laravel 4 as a base, but makes architecting larger applications with things like an application namespace out of the box. Laravel 4 applications will need a fair bit of work to be ported to Laravel 5. Features that are new or have been updated in Laravel 5 include: