本文實例講述了Laravel框架生命周期與原理。分享給大家供大家參考，具體如下：

引言：

如果你對一件工具的使用原理了如指掌，那么你在用這件工具的時候會充滿信心！

正文：

一旦用戶（瀏覽器）發送了一個HTTP請求，我們的apache或者nginx一般都轉到index.php，因此，之后的一系列步驟都是從index.php開始的，我們先來看一看這個文件代碼。

 ?phprequire __DIR__. /../bootstrap/autoload.php $app = require_once __DIR__. /../bootstrap/app.php |--------------------------------------------------------------------------| Run The Application|--------------------------------------------------------------------------| Once we have the application, we can handle the incoming request| through the kernel, and send the associated response back to| the client s browser allowing them to enjoy the creative| and wonderful application we have prepared for them.$kernel = $app- make(Illuminate/Contracts/Http/Kernel::html' target='_blank'>class);$response = $kernel- handle( $request = Illuminate/Http/Request::capture()$response- send();$kernel- terminate($request, $response);

作者在注釋里談了kernel的作用，kernel的作用，kernel處理來訪的請求，并且發送相應返回給用戶瀏覽器。

這里又涉及到了一個app對象，所以附上app對象，所以附上app對象的源碼，這份源碼是/bootstrap/app.php

 ?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;

請看app變量是Illuminate/Foundation/Application類的對象，所以調用了這個類的構造函數，具體做了什么事，我們看源碼。

public function __construct($basePath = null) if ($basePath) { $this- setBasePath($basePath); $this- registerBaseBindings(); $this- registerBaseServiceProviders(); $this- registerCoreContainerAliases();}

構造器做了3件事，前兩件事很好理解，創建Container，注冊了ServiceProvider，看代碼

/** * Register the basic bindings into the container. * @return voidprotected function registerBaseBindings() static::setInstance($this); $this- instance( app , $this); $this- instance(Container::class, $this); * Register all of the base service providers. * @return voidprotected function registerBaseServiceProviders() $this- register(new EventServiceProvider($this)); $this- register(new LogServiceProvider($this)); $this- register(new RoutingServiceProvider($this));}

最后一件事，是做了個很大的數組，定義了大量的別名，側面體現程序員是聰明的懶人。

/** * Register the core class aliases in the container. * @return voidpublic function registerCoreContainerAliases() $aliases = [ app = [/Illuminate/Foundation/Application::class, /Illuminate/Contracts/Container/Container::class, /Illuminate/Contracts/Foundation/Application::class], auth = [/Illuminate/Auth/AuthManager::class, /Illuminate/Contracts/Auth/Factory::class], auth.driver = [/Illuminate/Contracts/Auth/Guard::class], blade.compiler = [/Illuminate/View/Compilers/BladeCompiler::class], cache = [/Illuminate/Cache/CacheManager::class, /Illuminate/Contracts/Cache/Factory::class], cache.store = [/Illuminate/Cache/Repository::class, /Illuminate/Contracts/Cache/Repository::class], config = [/Illuminate/Config/Repository::class, /Illuminate/Contracts/Config/Repository::class], cookie = [/Illuminate/Cookie/CookieJar::class, /Illuminate/Contracts/Cookie/Factory::class, /Illuminate/Contracts/Cookie/QueueingFactory::class], encrypter = [/Illuminate/Encryption/Encrypter::class, /Illuminate/Contracts/Encryption/Encrypter::class], db = [/Illuminate/Database/DatabaseManager::class], db.connection = [/Illuminate/Database/Connection::class, /Illuminate/Database/ConnectionInterface::class], events = [/Illuminate/Events/Dispatcher::class, /Illuminate/Contracts/Events/Dispatcher::class], files = [/Illuminate/Filesystem/Filesystem::class], filesystem = [/Illuminate/Filesystem/FilesystemManager::class, /Illuminate/Contracts/Filesystem/Factory::class], filesystem.disk = [/Illuminate/Contracts/Filesystem/Filesystem::class], filesystem.cloud = [/Illuminate/Contracts/Filesystem/Cloud::class], hash = [/Illuminate/Contracts/Hashing/Hasher::class], translator = [/Illuminate/Translation/Translator::class, /Illuminate/Contracts/Translation/Translator::class], log = [/Illuminate/Log/Writer::class, /Illuminate/Contracts/Logging/Log::class, /Psr/Log/LoggerInterface::class], mailer = [/Illuminate/Mail/Mailer::class, /Illuminate/Contracts/Mail/Mailer::class, /Illuminate/Contracts/Mail/MailQueue::class], auth.password = [/Illuminate/Auth/Passwords/PasswordBrokerManager::class, /Illuminate/Contracts/Auth/PasswordBrokerFactory::class], auth.password.broker = [/Illuminate/Auth/Passwords/PasswordBroker::class, /Illuminate/Contracts/Auth/PasswordBroker::class], queue = [/Illuminate/Queue/QueueManager::class, /Illuminate/Contracts/Queue/Factory::class, /Illuminate/Contracts/Queue/Monitor::class], queue.connection = [/Illuminate/Contracts/Queue/Queue::class], queue.failer = [/Illuminate/Queue/Failed/FailedJobProviderInterface::class], redirect = [/Illuminate/Routing/Redirector::class], redis = [/Illuminate/Redis/RedisManager::class, /Illuminate/Contracts/Redis/Factory::class], request = [/Illuminate/Http/Request::class, /Symfony/Component/HttpFoundation/Request::class], router = [/Illuminate/Routing/Router::class, /Illuminate/Contracts/Routing/Registrar::class, /Illuminate/Contracts/Routing/BindingRegistrar::class], session = [/Illuminate/Session/SessionManager::class], session.store = [/Illuminate/Session/Store::class, /Illuminate/Contracts/Session/Session::class], url = [/Illuminate/Routing/UrlGenerator::class, /Illuminate/Contracts/Routing/UrlGenerator::class], validator = [/Illuminate/Validation/Factory::class, /Illuminate/Contracts/Validation/Factory::class], view = [/Illuminate/View/Factory::class, /Illuminate/Contracts/View/Factory::class], foreach ($aliases as $key = $aliases) { foreach ($aliases as $alias) { $this- alias($key, $alias);}

這里出現了一個instance函數，其實這并不是Application類的函數，而是Application類的父類Container類的函數

/** * Register an existing instance as shared in the container. * @param string $abstract * @param mixed $instance * @return voidpublic function instance($abstract, $instance) $this- removeAbstractAlias($abstract); unset($this- aliases[$abstract]); // We ll check to determine if this type has been bound before, and if it has // we will fire the rebound callbacks registered with the container and it // can be updated with consuming classes that have gotten resolved here. $this- instances[$abstract] = $instance; if ($this- bound($abstract)) { $this- rebound($abstract);}

Application是Container的子類，所以$app不僅是Application類的對象，還是Container的對象，所以，新出現的singleton函數我們就可以到Container類的源代碼文件里查。bind函數和singleton的區別見這篇博文。

singleton這個函數，前一個參數是實際類名，后一個參數是類的“別名”。

$app對象聲明了3個單例模型對象，分別是HttpKernel，ConsoleKernel，ExceptionHandler。請注意，這里并沒有創建對象，只是聲明，也只是起了一個“別名”。

大家有沒有發現，index.php中也有一個$kernel變量，但是只保存了make出來的HttpKernel變量，因此本文不再討論，ConsoleKernel，ExceptionHandler。。。

繼續在文件夾下找到App/Http/Kernel.php，既然我們把實際的HttpKernel做的事情都寫在這個php文件里，就從這份代碼里看看究竟做了哪些事？

 ?phpnamespace App/Http;use Illuminate/Foundation/Http/Kernel as HttpKernel;class Kernel extends HttpKernel * The application s global HTTP middleware stack. * These middleware are run during every request to your application. * @var array protected $middleware = [ /Illuminate/Foundation/Http/Middleware/CheckForMaintenanceMode::class, ///App/Http/Middleware/MyMiddleware::class, * The application s route middleware groups. * @var array protected $middlewareGroups = [ web = [ /App/Http/Middleware/EncryptCookies::class, /Illuminate/Cookie/Middleware/AddQueuedCookiesToResponse::class, /Illuminate/Session/Middleware/StartSession::class, /Illuminate/View/Middleware/ShareErrorsFromSession::class, /App/Http/Middleware/VerifyCsrfToken::class, api = [ throttle:60,1 , * The application s route middleware. * These middleware may be assigned to groups or used inpidually. * @var array protected $routeMiddleware = [ auth = /App/Http/Middleware/Authenticate::class, auth.basic = /Illuminate/Auth/Middleware/AuthenticateWithBasicAuth::class, guest = /App/Http/Middleware/RedirectIfAuthenticated::class, throttle = /Illuminate/Routing/Middleware/ThrottleRequests::class, mymiddleware = /App/Http/Middleware/MyMiddleware::class,}

一目了然，HttpKernel里定義了中間件數組。

該做的做完了，就開始了請求到響應的過程，見index.php

$response = $kernel- handle( $request = Illuminate/Http/Request::capture()$response- send();

最后在中止，釋放所有資源。

/*** Call the terminate method on any terminable middleware.* @param /Illuminate/Http/Request $request* @param /Illuminate/Http/Response $response* @return voidpublic function terminate($request, $response) $this- terminateMiddleware($request, $response); $this- app- terminate();}

總結一下，簡單歸納整個過程就是：

1.index.php加載/bootstrap/app.php，在Application類的構造函數中創建Container，注冊了ServiceProvider，定義了別名數組，然后用app變量保存構造函數構造出來的對象。

2.使用app這個對象，創建1個單例模式的對象HttpKernel，在創建HttpKernel時調用了構造函數，完成了中間件的聲明。

3.以上這些工作都是在請求來訪之前完成的，接下來開始等待請求，然后就是：接受到請求-- 處理請求-- 發送響應-- 中止app變量

以上就是本文的全部內容，希望對大家的學習有所幫助，更多相關內容請關注PHP ！

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