[TOC]  Laravel 的生命周期從`public\index.php`開始，從`public\index.php`結束。 ~~~php // 階段一 require __DIR__.'/../bootstrap/autoload.php'; // 階段二 $app = require_once __DIR__.'/../bootstrap/app.php'; $kernel = $app->make(Illuminate\Contracts\Http\Kernel::class); // 階段三 $response = $kernel->handle( $request = Illuminate\Http\Request::capture() ); $response->send(); // 其它 $kernel->terminate($request, $response); ~~~ ## **1. 加載項目依賴** 現代 PHP 依賴于 Composer 包管理器，入口文件通過引入由 Composer 包管理器自動生成的類加載程序，可以輕松注冊并加載項目所依賴的第三方組件庫。 所有組件的加載工作，僅需一行代碼即可完成： ~~~php require __DIR__.'/../vendor/autoload.php'; ~~~ ## **2. 創建 Laravel 應用實例** 創建應用實例（或服務容器），由位于 `bootstrap/app.php` 文件里的引導程序完成，創建服務容器的過程即為應用初始化的過程，項目初始化時包括：注冊項目基礎服務、注冊項目服務器提供的別名、注冊目錄路徑等在內的一些注冊工作。 下面是`bootstrap/app.php`的代碼，包含兩個主要部分「創建應用實例」和「綁定內核至 APP 服務容器」： ~~~php <?php // 第一部分： 創建應用實例 $app = new Illuminate\Foundation\Application( realpath(__DIR__.'/../') ); // 第二部分： 完成內核綁定 $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 $app; ~~~ ### **2.1 創建應用實例** 創建應用實例即實例化 `Illuminate\Foundation\Application` 這個服務容器（**APP容器**），其中包括：注冊應用的基礎路徑并將路徑綁定到 **APP容器**、注冊基礎服務提供者到**APP容器**、注冊核心容器別名到**APP容器** ~~~php /** * Create a new Illuminate application instance. * * @param string|null $basePath * @return void */ public function __construct($basePath = null) { if ($basePath) { $this->setBasePath($basePath); } $this->registerBaseBindings(); $this->registerBaseServiceProviders(); $this->registerCoreContainerAliases(); } ~~~ ### **2.2 內核綁定** Laravel 會依據 HTTP 請求的運行環境的不同，將請求發送至相應的內核： **HTTP 內核** 或 **Console 內核**。無論 HTTP 內核還是 Console 內核，它們的作用都是是接收一個 HTTP 請求，隨后返回一個響應。 ## **3. 接收請求并響應** ~~~php $kernel = $app->make(Illuminate\Contracts\Http\Kernel::class); $response = $kernel->handle( $request = Illuminate\Http\Request::capture() ); $response->send(); ~~~ ### **3.1 解析內核實例** 在第二階段我們已經將 **HTTP 內核** 和 **Console 內核** 綁定到了 **APP 容器**，使用時通過 APP 容器 的 `make() ` 方法將內核解析出來，解析的過程就是內核實例化的過程。 ~~~php $kernel = $app->make(Illuminate\Contracts\Http\Kernel::class); ~~~ 進一步挖掘 `Illuminate\Foundation\Http\Kernel` 內核的 `__construct(Illuminate\Contracts\Foundation\Application $app, \Illuminate\Routing\Router $router)` 構造方法，它接收 APP 容器 和 路由器 兩個參數。 ~~~php /** * Create a new HTTP kernel instance. * * @param \Illuminate\Contracts\Foundation\Application $app * @param \Illuminate\Routing\Router $router * @return void */ public function __construct(Application $app, Router $router) { $this->app = $app; $this->router = $router; $this->syncMiddlewareToRouter(); } ~~~ 在實例化內核時，構造函數內將在 HTTP 內核定義的「中間件組」注冊到 **路由器**，注冊完后就可以在實際處理 HTTP 請求前調用這些「中間件」實現 **過濾 請求**的目的。 ~~~php /** * Sync the current state of the middleware to the router. * * @return void */ protected function syncMiddlewareToRouter() { $this->router->middlewarePriority = $this->middlewarePriority; foreach ($this->middlewareGroups as $key => $middleware) { $this->router->middlewareGroup($key, $middleware); } foreach ($this->routeMiddleware as $key => $middleware) { $this->router->aliasMiddleware($key, $middleware); } } /** * Register a group of middleware. * * @param string $name * @param array $middleware * @return $this */ public function middlewareGroup($name, array $middleware) { $this->middlewareGroups[$name] = $middleware; return $this; } /** * Register a short-hand name for a middleware. * * @param string $name * @param string $class * @return $this */ public function aliasMiddleware($name, $class) { $this->middleware[$name] = $class; return $this; } ~~~ ### **3.2 處理 HTTP 請求** ~~~ // 處理請求 $response = $kernel->handle( // 創建請求實例 $request = Illuminate\Http\Request::capture() ); ~~~ * 創建請求實例 請求實例 `Illuminate\Http\Request` 的 `capture()` 方法內部通過 **Symfony** 實例創建一個 Laravel 請求實例。這樣我們就可以獲取到用戶請求報文的相關信息 ~~~ /** * Create a new Illuminate HTTP request from server variables. * * @class Illuminate\Http\Request * @return static */ public static function capture() { static::enableHttpMethodParameterOverride(); return static::createFromBase(SymfonyRequest::createFromGlobals()); } /** * Create an Illuminate request from a Symfony instance. * * @see https://github.com/symfony/symfony/blob/master/src/Symfony/Component/HttpFoundation/Request.php * @param \Symfony\Component\HttpFoundation\Request $request * @return \Illuminate\Http\Request */ public static function createFromBase(SymfonyRequest $request) { if ($request instanceof static) { return $request; } $content = $request->content; $request = (new static)->duplicate( $request->query->all(), $request->request->all(), $request->attributes->all(), $request->cookies->all(), $request->files->all(), $request->server->all() ); $request->content = $content; $request->request = $request->getInputSource(); return $request; } ~~~ * 處理請求 請求處理發生在 HTTP 內核 的 `handle()` 方法內。 `Illuminate\Foundation\Http\kernel.php` ~~~ /** * Handle an incoming HTTP request. * * @param \Illuminate\Http\Request $request * @return \Illuminate\Http\Response */ public function handle($request) { try { $request->enableHttpMethodParameterOverride(); $response = $this->sendRequestThroughRouter($request); } catch (Exception $e) { $this->reportException($e); $response = $this->renderException($request, $e); } catch (Throwable $e) { $this->reportException($e = new FatalThrowableError($e)); $response = $this->renderException($request, $e); } $this->app['events']->dispatch( new RequestHandled($request, $response) ); return $response; } ~~~ `handle()` 方法接收一個 HTTP 請求，并最終生成一個 HTTP 響應。 繼續深入到處理 HTTP 請求的方法**$this->sendRequestThroughRouter($request)**內部。 ~~~ /** * Send the given request through the middleware / router. * * @param \Illuminate\Http\Request $request * @return \Illuminate\Http\Response */ protected function sendRequestThroughRouter($request) { // 將 $request 實例注冊到APP 容器供后續使用； $this->app->instance('request', $request); // 清除之前 $request 實例緩存 Facade::clearResolvedInstance('request'); // 啟動「引導程序」 $this->bootstrap(); // 發送請求至路由 return (new Pipeline($this->app)) ->send($request) ->through($this->app->shouldSkipMiddleware() ? [] : $this->middleware) ->then($this->dispatchToRouter()); } ~~~ ## **4. 發送響應** 發送響應由 `Illuminate\Http\Response` 父類 `Symfony\Component\HttpFoundation\Response` 中的 `send()` 方法完成。 ~~~php /** * Sends HTTP headers and content. * * @return $this */ public function send() { // 發送響應頭部信息 $this->sendHeaders(); // 發送報文主題 $this->sendContent(); if (\function_exists('fastcgi_finish_request')) { fastcgi_finish_request(); } elseif (!\in_array(\PHP_SAPI, ['cli', 'phpdbg'], true)) { static::closeOutputBuffers(0, true); } return $this; } ~~~ ## **5. 終止程序** 程序終止，完成終止中間件的調用 `Illuminate/Foundation/Http/Kernel.php` ~~~ /** * Call the terminate method on any terminable middleware. * * @param \Illuminate\Http\Request $request * @param \Illuminate\Http\Response $response * @return void */ public function terminate($request, $response) { $this->terminateMiddleware($request, $response); $this->app->terminate(); } /** * Call the terminate method on any terminable middleware. * * @param \Illuminate\Http\Request $request * @param \Illuminate\Http\Response $response * @return void */ protected function terminateMiddleware($request, $response) { $middlewares = $this->app->shouldSkipMiddleware() ? [] : array_merge( $this->gatherRouteMiddleware($request), $this->middleware ); foreach ($middlewares as $middleware) { if (! is_string($middleware)) { continue; } [$name] = $this->parseMiddleware($middleware); $instance = $this->app->make($name); if (method_exists($instance, 'terminate')) { $instance->terminate($request, $response); } } } ~~~ ***** > 詳見：https://learnku.com/articles/10421/depth-mining-of-laravel-life-cycle