聽說過 Laravel 近幾年很火，之前也接觸過 YII 2，CodeIgniter 3，Symfony 等 php 框架，一直沒有機會學習 Laravel。現在公司計劃轉向 Laravel 框架，廢話少說，趕緊學起來。
Laravel 框架，當然也是一個基於 composer 工具管理依賴包的開源項目。初看 Laravel 框架代碼就可以發現，整體架構耦合度小，開發比較靈活。在 Laravel 框架下，一次請求的生命週期可以用下面的流程圖來概括。
下面，主要從以下幾個方面分析框架：
一、Laravel 框架生命週期流程圖分析
二、Laravel 框架底層概念理解
（1）服務容器
（2）服務提供者
（3）門面
（4）契約
（5）管道
（6）事件
（7）廣播
一、Laravel 框架生命週期流程圖分析（見上圖）
圖中比較詳細地畫出了一次請求下整個框架的生命週期，下面主要從幾個重要的生命時期進行分析。
（1）構造應用程序框架，即服務容器
在構造應用程序框架過程中，主要完成以下方面工作：
（a）設置基本路徑，即綁定所有應用程序路徑到容器中，包括：
/**
* Bind all of the application paths in the container.
*
* @return void
*/
protected function bindPathsInContainer()
{
$this->instance('path', $this->path()); //app目錄
$this->instance('path.base', $this->basePath()); //根目錄
$this->instance('path.lang', $this->langPath()); //語言包目錄
$this->instance('path.config', $this->configPath()); //配置文件目錄
$this->instance('path.public', $this->publicPath()); //對外公開目錄
$this->instance('path.storage', $this->storagePath()); //文件存儲目錄
$this->instance('path.database', $this->databasePath()); //數據庫配置目錄
$this->instance('path.resources', $this->resourcePath()); //前端資源目錄
$this->instance('path.bootstrap', $this->bootstrapPath()); //啓動目錄
}
（b）將基本綁定註冊到容器中，包括：
/**
* Register the basic bindings into the container.
*
* @return void
*/
protected function registerBaseBindings()
{
static::setInstance($this); //將自身設置爲服務容器
$this->instance('app', $this); //綁定應用對象，別名爲 'app'
$this->instance(Container::class, $this); //綁定應用對象，別名爲 Container::class
$this->singleton(Mix::class); //註冊一個 Mix 單例類，別名爲 Mix::class
$this->instance(PackageManifest::class, new PackageManifest(
new Filesystem, $this->basePath(), $this->getCachedPackagesPath()
)); //綁定應用對象，別名爲 PackageManifest::class
}
（c）註冊所有基本服務提供者（事件、日誌和路由），包括：
/**
* Register all of the base service providers.
*
* @return void
*/
protected function registerBaseServiceProviders()
{
$this->register(new EventServiceProvider($this));
$this->register(new LogServiceProvider($this));
$this->register(new RoutingServiceProvider($this));
}
<?php
namespace Illuminate\Events;
use Illuminate\Contracts\Queue\Factory as QueueFactoryContract;
use Illuminate\Support\ServiceProvider;
class EventServiceProvider extends ServiceProvider
{
/**
* Register the service provider.
* 註冊一個任務分發器的單例類，別名爲 'events'，用於處理容器中所有的隊列任務
*
* @return void
*/
public function register()
{
$this->app->singleton('events', function ($app) {
return (new Dispatcher($app))->setQueueResolver(function () use ($app) {
return $app->make(QueueFactoryContract::class);
});
});
}
}
<?php
namespace Illuminate\Log;
use Illuminate\Support\ServiceProvider;
class LogServiceProvider extends ServiceProvider
{
/**
* Register the service provider.
* 註冊一個記錄日誌的單例類，別名爲 'log'
*
* @return void
*/
public function register()
{
$this->app->singleton('log', function ($app) {
return new LogManager($app);
});
}
}
<?php
namespace Illuminate\Routing;
use Exception;
use Illuminate\Contracts\Routing\ResponseFactory as ResponseFactoryContract;
use Illuminate\Contracts\Routing\UrlGenerator as UrlGeneratorContract;
use Illuminate\Contracts\View\Factory as ViewFactoryContract;
use Illuminate\Routing\Contracts\ControllerDispatcher as ControllerDispatcherContract;
use Illuminate\Support\ServiceProvider;
use Nyholm\Psr7\Factory\Psr17Factory;
use Nyholm\Psr7\Response as PsrResponse;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Symfony\Bridge\PsrHttpMessage\Factory\PsrHttpFactory;
class RoutingServiceProvider extends ServiceProvider
{
/**
* Register the service provider.
* 註冊多個類，具體見下面註釋
*
* @return void
*/
public function register()
{
$this->registerRouter(); //註冊路由器單例類，別名爲 'router'
$this->registerUrlGenerator(); //註冊路由產生器單例類，別名爲 'url'
$this->registerRedirector(); //註冊重定向單例類，別名爲 'redirect'
$this->registerPsrRequest(); //註冊一個PSR-7請求類，別名爲 ServerRequestInterface::class
$this->registerPsrResponse(); //註冊一個PSR-7響應類，別名爲 ResponseInterface::class
$this->registerResponseFactory(); //註冊響應工廠單例類，別名爲 ResponseFactoryContract::class，用於處理重定向對象 redirect
$this->registerControllerDispatcher(); //註冊控制器分發單例類，別名爲 ControllerDispatcherContract::class
}
...
}
（d）在容器中註冊核心類別名，包括：
/**
* Register the core class aliases in the container.
*
* @return void
*/
public function registerCoreContainerAliases()
{
foreach ([
'app' => [self::class, \Illuminate\Contracts\Container\Container::class, \Illuminate\Contracts\Foundation\Application::class, \Psr\Container\ContainerInterface::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, \Psr\SimpleCache\CacheInterface::class],
'cache.psr6' => [\Symfony\Component\Cache\Adapter\Psr16Adapter::class, \Symfony\Component\Cache\Adapter\AdapterInterface::class, \Psr\Cache\CacheItemPoolInterface::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, \Illuminate\Database\ConnectionResolverInterface::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\Hashing\HashManager::class],
'hash.driver' => [\Illuminate\Contracts\Hashing\Hasher::class],
'translator' => [\Illuminate\Translation\Translator::class, \Illuminate\Contracts\Translation\Translator::class],
'log' => [\Illuminate\Log\LogManager::class, \Psr\Log\LoggerInterface::class],
'mail.manager' => [\Illuminate\Mail\MailManager::class, \Illuminate\Contracts\Mail\Factory::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],
'redis.connection' => [\Illuminate\Redis\Connections\Connection::class, \Illuminate\Contracts\Redis\Connection::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],
] as $key => $aliases) {
foreach ($aliases as $alias) {
$this->alias($key, $alias);
}
}
}
（2）處理HTTP請求 $response = (App\Http\Kernel) $kernel->handle($request);
（A）依次啓動 App\Http\Kernel :: $bootstrappers 中定義的類，見代碼：
/**
* The bootstrap classes for the application.
*
* @var array
*/
protected $bootstrappers = [
\Illuminate\Foundation\Bootstrap\LoadEnvironmentVariables::class,
\Illuminate\Foundation\Bootstrap\LoadConfiguration::class,
\Illuminate\Foundation\Bootstrap\HandleExceptions::class,
\Illuminate\Foundation\Bootstrap\RegisterFacades::class,
\Illuminate\Foundation\Bootstrap\RegisterProviders::class,
\Illuminate\Foundation\Bootstrap\BootProviders::class,
];
（a）加載環境變量類 LoadEnvironmentVariables::bootstrap();
<?php
namespace Illuminate\Foundation\Bootstrap;
use Dotenv\Dotenv;
use Dotenv\Exception\InvalidFileException;
use Illuminate\Contracts\Foundation\Application;
use Illuminate\Support\Env;
use Symfony\Component\Console\Input\ArgvInput;
use Symfony\Component\Console\Output\ConsoleOutput;
class LoadEnvironmentVariables
{
/**
* Bootstrap the given application.
*
* @param \Illuminate\Contracts\Foundation\Application $app
* @return void
*/
public function bootstrap(Application $app)
{
if ($app->configurationIsCached()) {
return;
}
$this->checkForSpecificEnvironmentFile($app);
try {
$this->createDotenv($app)->safeLoad();
} catch (InvalidFileException $e) {
$this->writeErrorAndDie($e);
}
}
...
}
（b）加載配置類 LoadConfiguration::bootstrap();
<?php
namespace Illuminate\Foundation\Bootstrap;
use Exception;
use Illuminate\Config\Repository;
use Illuminate\Contracts\Config\Repository as RepositoryContract;
use Illuminate\Contracts\Foundation\Application;
use SplFileInfo;
use Symfony\Component\Finder\Finder;
class LoadConfiguration
{
/**
* Bootstrap the given application.
*
* @param \Illuminate\Contracts\Foundation\Application $app
* @return void
*/
public function bootstrap(Application $app)
{
$items = [];
// First we will see if we have a cache configuration file. If we do, we'll load
// the configuration items from that file so that it is very quick. Otherwise
// we will need to spin through every configuration file and load them all.
if (file_exists($cached = $app->getCachedConfigPath())) {
$items = require $cached;
$loadedFromCache = true;
}
// Next we will spin through all of the configuration files in the configuration
// directory and load each one into the repository. This will make all of the
// options available to the developer for use in various parts of this app.
$app->instance('config', $config = new Repository($items));
if (! isset($loadedFromCache)) {
$this->loadConfigurationFiles($app, $config);
}
// Finally, we will set the application's environment based on the configuration
// values that were loaded. We will pass a callback which will be used to get
// the environment in a web context where an "--env" switch is not present.
$app->detectEnvironment(function () use ($config) {
return $config->get('app.env', 'production');
});
date_default_timezone_set($config->get('app.timezone', 'UTC'));
mb_internal_encoding('UTF-8');
}
...
}
（c）處理異常類 HandleExceptions::bootstrap();
<?php
namespace Illuminate\Foundation\Bootstrap;
use ErrorException;
use Exception;
use Illuminate\Contracts\Debug\ExceptionHandler;
use Illuminate\Contracts\Foundation\Application;
use Symfony\Component\Console\Output\ConsoleOutput;
use Symfony\Component\ErrorHandler\Error\FatalError;
use Throwable;
class HandleExceptions
{
/**
* Reserved memory so that errors can be displayed properly on memory exhaustion.
*
* @var string
*/
public static $reservedMemory;
/**
* The application instance.
*
* @var \Illuminate\Contracts\Foundation\Application
*/
protected $app;
/**
* Bootstrap the given application.
*
* @param \Illuminate\Contracts\Foundation\Application $app
* @return void
*/
public function bootstrap(Application $app)
{
self::$reservedMemory = str_repeat('x', 10240);
$this->app = $app;
error_reporting(-1);
set_error_handler([$this, 'handleError']);
set_exception_handler([$this, 'handleException']);
register_shutdown_function([$this, 'handleShutdown']);
if (! $app->environment('testing')) {
ini_set('display_errors', 'Off');
}
}
...
}
（d）註冊外觀服務類 RegisterFacades::bootstrap();
<?php
namespace Illuminate\Foundation\Bootstrap;
use Illuminate\Contracts\Foundation\Application;
use Illuminate\Foundation\AliasLoader;
use Illuminate\Foundation\PackageManifest;
use Illuminate\Support\Facades\Facade;
class RegisterFacades
{
/**
* Bootstrap the given application.
*
* @param \Illuminate\Contracts\Foundation\Application $app
* @return void
*/
public function bootstrap(Application $app)
{
Facade::clearResolvedInstances();
Facade::setFacadeApplication($app);
AliasLoader::getInstance(array_merge(
$app->make('config')->get('app.aliases', []),
$app->make(PackageManifest::class)->aliases()
))->register();
}
}
（e）註冊服務提供者類 RegisterProviders::bootstrap();
註冊 config/app.php 下配置項 providers 中的所有服務提供者
<?php
namespace Illuminate\Foundation\Bootstrap;
use Illuminate\Contracts\Foundation\Application;
class RegisterProviders
{
/**
* Bootstrap the given application.
*
* @param \Illuminate\Contracts\Foundation\Application $app
* @return void
*/
public function bootstrap(Application $app)
{
$app->registerConfiguredProviders();
}
}
（f）啓動服務提供者類 BootProviders::bootstrap();
啓動應用程序 $app->boot();
<?php
namespace Illuminate\Foundation;
use Closure;
use Illuminate\Container\Container;
use Illuminate\Contracts\Foundation\Application as ApplicationContract;
use Illuminate\Contracts\Foundation\CachesConfiguration;
use Illuminate\Contracts\Foundation\CachesRoutes;
use Symfony\Component\HttpKernel\HttpKernelInterface;
class Application extends Container implements ApplicationContract, CachesConfiguration, CachesRoutes, HttpKernelInterface
{
...
/**
* Boot the application's service providers.
*
* @return void
*/
public function boot()
{
if ($this->isBooted()) {
return;
}
// Once the application has booted we will also fire some "booted" callbacks
// for any listeners that need to do work after this initial booting gets
// finished. This is useful when ordering the boot-up processes we run.
$this->fireAppCallbacks($this->bootingCallbacks);
array_walk($this->serviceProviders, function ($p) {
$this->bootProvider($p);
});
$this->booted = true;
$this->fireAppCallbacks($this->bootedCallbacks);
}
...
}
（B）通過管道處理 Http 中間件，然後繼續分發路由
<?php
namespace Illuminate\Foundation\Http;
use Exception;
use Illuminate\Contracts\Http\Kernel as KernelContract;
use Illuminate\Foundation\Http\Events\RequestHandled;
use Illuminate\Routing\Pipeline;
use Illuminate\Routing\Router;
use Illuminate\Support\Facades\Facade;
use InvalidArgumentException;
use Symfony\Component\Debug\Exception\FatalThrowableError;
use Throwable;
class Kernel implements KernelContract
{
...
/**
* Send the given request through the middleware / router.
*
* @param \Illuminate\Http\Request $request
* @return \Illuminate\Http\Response
*/
protected function sendRequestThroughRouter($request)
{
$this->app->instance('request', $request);
Facade::clearResolvedInstance('request');
$this->bootstrap();
return (new Pipeline($this->app))
->send($request)
->through($this->app->shouldSkipMiddleware() ? [] : $this->middleware)
->then($this->dispatchToRouter());
}
...
}
在處理中間件過程中，先處理全局中間件，再處理分組中間件（如api，web，...），最後處理路由中間件，最後請求被指派到某個控制器中。
二、Laravel 框架底層概念理解
未完，待續...
在一個服務提供者中， 可以通過 $this->app 變量訪問容器；
在任何地方都可以調用 function app($abstract = null, array $parameters = []) 輔助函數獲取服務容器及其對象；
也可以使用 \Illuminate\Container\Container::getInstance(); 獲取服務容器，使用 Container::getInstance()->make($abstract, $parameters); 解析服務容器對象。