为WEB艺术家创造的框架
由SitePoint发起的2015年最流行WEB框架的调查中，Laravel已巨大的优势获得了商用使用 数量、个人项目使用数量的第一名。当之无愧是目前最好的WEB框架之一。那么就让我们来 一步一步探究这样优秀的框架究竟是如何实现的吧。
目录
- 入口文件 index.php
- Illuminate\Foundation\Application 类
- 注入所有基础 Service Provider
入口文件 index.php
一个基于Laravel的应用，当WEB服务器接受到来自外部的请求后，会将这个这个请求解析到 应用根目录的 public/index.php 中。
Laravel源码解读-index.php (laravel_index.php)download
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<?php/** * Laravel - A PHP Framework For Web Artisans * * @package Laravel * @author Taylor Otwell <taylorotwell@gmail.com> *//*|--------------------------------------------------------------------------| Register The Auto Loader|--------------------------------------------------------------------------|| Composer provides a convenient, automatically generated class loader for| our application. We just need to utilize it! We'll simply require it| into the script here so that we don't have to worry about manual| loading any of our classes later on. It feels nice to relax.|*/require __DIR__.'/../bootstrap/autoload.php';/*|--------------------------------------------------------------------------| Turn On The Lights|--------------------------------------------------------------------------|| We need to illuminate PHP development, so let us turn on the lights.| This bootstraps the framework and gets it ready for use, then it| will load up this application so that we can run it and send| the responses back to the browser and delight our users.|*/$app = require_once __DIR__.'/../bootstrap/app.php';/*|--------------------------------------------------------------------------| Run The Application|--------------------------------------------------------------------------|| Once we have the application, we can handle the incoming request| through the kernel, and send the associated response back to| the client's browser allowing them to enjoy the creative| and wonderful application we have prepared for them.|*/$kernel = $app->make(Illuminate\Contracts\Http\Kernel::class);$response = $kernel->handle( $request = Illuminate\Http\Request::capture());$response->send();$kernel->terminate($request, $response);
第二十一行代码
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require __DIR__.'/../bootstrap/autoload.php';
为Laravel应用引入了由Composer提供的类加载器，这样Laravel应用便无需再手动加载任 何的类。其加载原理不是此次探究的目标，所以仅仅这样使用就好了。接下的代码，便是重 点。
Illuminate\Foundation\Application 类
该类的继承结构如下：
第三十五行代码
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$app = require_once __DIR__.'/../bootstrap/app.php';
它将我的视线引入到了另外一个文件中，去看看到底发生了什么吧。
Laravel源码解读-app.php (laravel_app.php)download
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<?php/*|--------------------------------------------------------------------------| Create The Application|--------------------------------------------------------------------------|| The first thing we will do is create a new Laravel application instance| which serves as the "glue" for all the components of Laravel, and is| the IoC container for the system binding all of the various parts.|*/$app = new Illuminate\Foundation\Application( realpath(__DIR__.'/../'));/*|--------------------------------------------------------------------------| Bind Important Interfaces|--------------------------------------------------------------------------|| Next, we need to bind some important interfaces into the container so| we will be able to resolve them when needed. The kernels serve the| incoming requests to this application from both the web and CLI.|*/$app->singleton( Illuminate\Contracts\Http\Kernel::class, App\Http\Kernel::class);$app->singleton( Illuminate\Contracts\Console\Kernel::class, App\Console\Kernel::class);$app->singleton( Illuminate\Contracts\Debug\ExceptionHandler::class, App\Exceptions\Handler::class);/*|--------------------------------------------------------------------------| Return The Application|--------------------------------------------------------------------------|| This script returns the application instance. The instance is given to| the calling script so we can separate the building of the instances| from the actual running of the application and sending responses.|*/return $app;
看第十四行，原来$app是一个 Illuminate\Foundation\Application 对象，那么在创 建这个对象的时候又发生了什么呢？
从它的构造方法看起：
Illuminate\Foundation\Application 构造方法123456789101112131415161718
/** * Create a new Illuminate application instance. * * @param string|null $basePath * @return void */public function __construct($basePath = null){ $this->registerBaseBindings(); $this->registerBaseServiceProviders(); $this->registerCoreContainerAliases(); if ($basePath) { $this->setBasePath($basePath); }}
顺着函数调用，往下看。在这个构造函数中，首先调用了registerBaseBindings方法。
Illuminate\Foundation\Application#registerBaseBindings12345678910111213
/** * Register the basic bindings into the container. * * @return void */protected function registerBaseBindings(){ static::setInstance($this); $this->instance('app', $this); $this->instance('Illuminate\Container\Container', $this);}
这段代码，是将实例对象注入到容器中。那么，这个容器是什么呢？答案还是要从这段调用 中去寻找。
static::setInstance($this) 所做的就是将 $this 赋值给自身的 instance 静态变 量。重点看 $this->instance('app', $this)。
instance 函数的作用是绑定一个已有对象到容器中，这个对象在容器中共享并且可以通 过键获取。
Illuminate\Container\Container#instance1234567891011121314151617181920212223242526272829
/** * Register an existing instance as shared in the container. * * @param string $abstract * @param mixed $instance * @return void */public function instance($abstract, $instance){ if (is_array($abstract)) { // $abstract 是这样的一个数组 ['actual key' => 'alias'] list($abstract, $alias) = $this->extractAlias($abstract); // 实际上的行为是 $this->aliases[$alias] = $abstract; $this->alias($abstract, $alias); } unset($this->aliases[$abstract]); // 检查是否有这个键是否已经注册到容器中 // $bound 是一个boolean值 $bound = $this->bound($abstract); $this->instances[$abstract] = $instance; if ($bound) { $this->rebound($abstract); }}
视线重新回到Application类中，接下来调用了这个方法 $this->registerBaseServiceProviders()，
Illuminate\Foundation\Application#registerBaseServiceProviders1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253
/** * Register all of the base service providers. * * @return void */protected function registerBaseServiceProviders(){ $this->register(new EventServiceProvider($this)); $this->register(new RoutingServiceProvider($this));}/** * Register a service provider with the application. * * @param \Illuminate\Support\ServiceProvider|string $provider * @param array $options * @param bool $force * @return \Illuminate\Support\ServiceProvider */public function register($provider, $options = [], $force = false){ if ($registered = $this->getProvider($provider) && !$force) { return $registered; } // If the given "provider" is a string, we will resolve it, passing in the // application instance automatically for the developer. This is simply // a more convenient way of specifying your service provider classes. if (is_string($provider)) { $provider = $this->resolveProviderClass($provider); } $provider->register(); // Once we have registered the service we will iterate through the options // and set each of them on the application so they will be available on // the actual loading of the service objects and for developer usage. foreach ($options as $key => $value) { $this[$key] = $value; } $this->markAsRegistered($provider); // If the application has already booted, we will call this boot method on // the provider class so it has an opportunity to do its boot logic and // will be ready for any usage by the developer's application logics. if ($this->booted) { $this->bootProvider($provider); } return $provider;}
其中，EventServiceProvider和RoutingServiceProvider分别是
Illuminate\Events\EventServiceProviderIlluminate\Routing\RoutingServiceProvider
这些ServiceProvider是 Illuminate\Support\ServiceProvider 的子类，它接受一个 Application 对象作为构造函数参数，存储在实例变量 $app 中。
注入所有基础 Service Provider
在 register 方法中，每个ServiceProvider被调用了自身的 register 方法。首先看 看 EventServiceProvider 中的吧。
Illuminate\Events\EventServiceProvider#register12345678
public function register(){ $this->app->singleton('events', function ($app) { return (new Dispatcher($app))->setQueueResolver(function () use ($app) { return $app->make('Illuminate\Contracts\Queue\Factory'); }); });}
上面方法体将一个 Illuminate\Events\Dispatcher 对象以键 events 绑定到了容器 中，它负责实现事件的调度。
再看看 Illuminate\Routing\RoutingServiceProvider:
Illuminate\Routing\RoutingServiceProvider#register1234567891011121314
public function register(){ $this->registerRouter(); $this->registerUrlGenerator(); $this->registerRedirector(); $this->registerPsrRequest(); $this->registerPsrResponse(); $this->registerResponseFactory();}
首页是在Laravel中接触的最多的 route 被注册，它是 Illuminate\Routing\Router 对象。
