Laravel如何加载PHP文件

The first three lines of database\seeds\DatabaseSeeder.php are:

<?php

use Illuminate\Database\Seeder;

class DatabaseSeeder extends Seeder { ... }

The Illuminate\Database\Seeder namespace points to vendor/laravel/framework/src/Illuminate/Database/Seeder.php.

How does Laravel require the files from relatively complex directory structures so easily just by using its namespaces?

Where are the files are actually loaded with require (like: require 'path\to\file';)?

It uses psr loader check this link

Laravel

Laravel uses PSR-4 autoloading via Composer to load files. Mainly, composer manages how classes and files are loaded.

Custom Framework

Most PHP frameworks today, like Laravel, use spl_autoload_register() to handle the dynamic loading of class files when a class has not been loaded. PSR-4 is a community standard from the PHP-FIG used to describe the format of classes and how their files should be written.

The PHP-FIG has example autoloaders you can modify for your own projects.

Relevant links

• http://php.net/manual/en/language.oop5.autoload.php
• http://www.php-fig.org/psr/psr-4/
• https://getcomposer.org/
• https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-4-autoloader-examples.md

If you open the index.php file you will see there in line 22:

require __DIR__.'/../bootstrap/autoload.php';

This require the autoload.php file, which loads the composer autoloader:

require __DIR__.'/../vendor/autoload.php';

Which handles all the automatic loading of the different files (classes/libraries).