摘要：實例化各服務提供者，根據其屬性將服務進行分類延遲服務即時服務，從而得到一個數組格式如，延遲處理注冊延遲的服務，以后再進行調用注冊延遲的事件即時處理直接進行注冊調用等，并重新寫入到，然后根據此文件進行相應的處理。

protected function sendRequestThroughRouter($request)
{
    # $this->app->instance("request", $request);

    # Facade::clearResolvedInstance("request");
    // 主要是這句代碼
    $this->bootstrap();

    # return (new Pipeline($this->app))
    #            ->send($request)
    #            ->through($this->app->shouldSkipMiddleware() ? [] : $this->middleware)
    #            ->then($this->dispatchToRouter());
}
public function bootstrap()
{
    if (! $this->app->hasBeenBootstrapped()) {
        $this->app->bootstrapWith($this->bootstrappers());
    }
}
protected function bootstrappers()
{
    #####################################################################
    #$bootstrappers = [
    #    IlluminateFoundationBootstrapLoadEnvironmentVariables::class,
    #    IlluminateFoundationBootstrapLoadConfiguration::class,
    #    IlluminateFoundationBootstrapHandleExceptions::class,      
    #    IlluminateFoundationBootstrapRegisterFacades::class,
    #    IlluminateFoundationBootstrapRegisterProviders::class,      
    #    IlluminateFoundationBootstrapBootProviders::class,
    #];
    #####################################################################
    return $this->bootstrappers;
}
public function bootstrapWith(array $bootstrappers)
{
    $this->hasBeenBootstrapped = true;

    foreach ($bootstrappers as $bootstrapper) {
        $this["events"]->fire("bootstrapping: ".$bootstrapper, [$this]);

        $this->make($bootstrapper)->bootstrap($this);

        $this["events"]->fire("bootstrapped: ".$bootstrapper, [$this]);
    }
}

$this->make($bootstrapper)->bootstrap($this)：會先創建$bootstrapper對象，在執行對象的引導方法，參數為應用對象

加載并設置應用的系統環境變量(IlluminateFoundationBootstrapLoadEnvironmentVariables)

public function bootstrap(Application $app)
{
    // /var/www/laravel/bootstrap/cache/config.php 存在則直接返回
    if ($app->configurationIsCached()) {
        return;
    }

    $this->checkForSpecificEnvironmentFile($app);

    try {
        // 委托Dotenv來臨時設置此次請求的系統環境變量，默認傳參依次為"/var/www/laravel"和".env"
        (new Dotenv($app->environmentPath(), $app->environmentFile()))->load();
    } catch (InvalidPathException $e) {
        //
    }
}
protected function checkForSpecificEnvironmentFile($app)
{
    // cli模式下，并且存在--env參數（類似命令為： cammond --env=example）
    if (php_sapi_name() == "cli" && with($input = new ArgvInput)->hasParameterOption("--env")) {
        // 將系統環境文件(類似：/var/www/laravel/.env.example)設置為$app應用的environmentFile屬性，供后面使用
        $this->setEnvironmentFilePath(
            $app, $app->environmentFile().".".$input->getParameterOption("--env")
        );
    }

    if (! env("APP_ENV")) {
        return;
    }

    $this->setEnvironmentFilePath(
        $app, $app->environmentFile().".".env("APP_ENV")
    );
}

(new Dotenv($app->environmentPath(), $app->environmentFile()))->load()

public function __construct($path, $file = ".env")
{
    // 類似/var/www/laravel/.env
    $this->filePath = $this->getFilePath($path, $file);
    // 創建加載器，委托Loader處理
    $this->loader = new Loader($this->filePath, true);
}
protected function getFilePath($path, $file)
{
    if (!is_string($file)) {
        $file = ".env";
    }

    $filePath = rtrim($path, DIRECTORY_SEPARATOR).DIRECTORY_SEPARATOR.$file;

    return $filePath;
}
public function load()
{
    return $this->loadData();
}
protected function loadData($overload = false)
{
    $this->loader = new Loader($this->filePath, !$overload);

    return $this->loader->load();
}

new Loader($this->filePath, !$overload)

public function __construct($filePath, $immutable = false)
{
    $this->filePath = $filePath;
    $this->immutable = $immutable;
}
public function load()
{
    $this->ensureFileIsReadable();

    $filePath = $this->filePath;
    $lines = $this->readLinesFromFile($filePath);
    foreach ($lines as $line) {
        // 如果行不是注釋行且含有=號，則進行
        if (!$this->isComment($line) && $this->looksLikeSetter($line)) {
            $this->setEnvironmentVariable($line);
        }
    }

    return $lines;
}
// 將文件按行的形式讀入到數組并返回
protected function readLinesFromFile($filePath)
{
    $autodetect = ini_get("auto_detect_line_endings");
    ini_set("auto_detect_line_endings", "1");
    $lines = file($filePath, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
    ini_set("auto_detect_line_endings", $autodetect);

    return $lines;
}
public function setEnvironmentVariable($name, $value = null)
{
    // 檢測過濾校驗環境變量
    list($name, $value) = $this->normaliseEnvironmentVariable($name, $value);
    // 當immutable為真時，不覆蓋對應的環境變量
    if ($this->immutable && $this->getEnvironmentVariable($name) !== null) {
        return;
    }
    // apache運行環境下，嘗試臨時覆蓋系統環境變量
    if (function_exists("apache_getenv") && function_exists("apache_setenv") && apache_getenv($name)) {
        apache_setenv($name, $value);
    }
    // 嘗試臨時設置當前請求的系統環境變量
    if (function_exists("putenv")) {
        putenv("$name=$value");
    }
    // 賦值全局變量
    $_ENV[$name] = $value;
    $_SERVER[$name] = $value;
}

將應用配置文件目錄(/var/www/laravel/config)下所有php文件返回的數組載入到$config對象(IlluminateFoundationBootstrapLoadConfiguration)

public function bootstrap(Application $app)
{
    $items = [];
    // /var/www/laravel/bootstrap/cache/config.php文件[配置文件的緩存合集，加快加載速度]存在則載入，并標記已加載
    if (file_exists($cached = $app->getCachedConfigPath())) {
        $items = require $cached;

        $loadedFromCache = true;
    }
    // 構建config對象，并注入到服務容器
    $app->instance("config", $config = new Repository($items));

    if (! isset($loadedFromCache)) {
        // 將系統的配置文件載入到$config對象
        $this->loadConfigurationFiles($app, $config);
    }
    // 設置$this["env"]為系統環境變量app.env,沒有則默認為production
    $app->detectEnvironment(function () use ($config) {
        return $config->get("app.env", "production");
    });

    date_default_timezone_set($config->get("app.timezone", "UTC"));

    mb_internal_encoding("UTF-8");
}

$config = new IlluminateConfigRepository($items)
public function __construct(array $items = [])
{
    $this->items = $items;
}

protected function loadConfigurationFiles(Application $app, RepositoryContract $repository)
{
    foreach ($this->getConfigurationFiles($app) as $key => $path) {
        // 此操作將在$repository對象里面構造一個多維數組屬性$this->items，值為相應的系統配置文件返回的數組，后續可以直接通過get獲取
        $repository->set($key, require $path);
    }
}
/** $files數組形式如下
    [
        "app" => "/var/www/laravel/config/app.php",
        "auth" => "/var/www/laravel/config/auth.php",
        "xx.file" => "/var/www/laravel/config/xx/file.php",
        "xx.yy.file" => "/var/www/laravel/config/xx/yy/file.php",
    ]
*/
protected function getConfigurationFiles(Application $app)
{
    $files = [];
    // 系統配置文件的路徑(/var/www/laravel/config)
    $configPath = realpath($app->configPath());
    // 文件相關的操作委托給Finder類(很強大)來處理，Finder實現了IteratorAggregate的getIterator方法
    foreach (Finder::create()->files()->name("*.php")->in($configPath) as $file) {
        // 迭代/var/www/laravel/config下面嵌套的層層子目錄構造成.形式的目錄
        $directory = $this->getNestedDirectory($file, $configPath);
        
        $files[$directory.basename($file->getRealPath(), ".php")] = $file->getRealPath();
    }

    return $files;
}

$repository->set($key, require $path)
// 構造將.形式轉變為相應層級的數組$this->items。比如：$key="xx.yy.file",$value="/var/www/laravel/config/xx/yy/file.php"，將會構建為:$this->items["xx"]["yy"]["file"] = $value返回的數組。
public function set($key, $value = null)
{
    $keys = is_array($key) ? $key : [$key => $value];

    foreach ($keys as $key => $value) {
        Arr::set($this->items, $key, $value);
    }
}

根據默認的系統配置文件目錄，以上操作的結果如下：
$config對象（new Repository）里面的$this->items數組屬性，后期可以通過$config->get()來獲取

$this->items["app"] = /var/www/laravel/config/app.php返回的數組;
$this->items["auth"] = /var/www/laravel/config/auth.php返回的數組;
$this->items["broadcasting"] = /var/www/laravel/config/broadcasting.php返回的數組;
$this->items["cache"] = /var/www/laravel/config/cache.php返回的數組;
$this->items["database"] = /var/www/laravel/config/database.php返回的數組;
$this->items["filesystems"] = /var/www/laravel/config/filesystems.php返回的數組;
$this->items["mail"] = /var/www/laravel/config/mail.php返回的數組;
$this->items["queue"] = /var/www/laravel/config/queue.php返回的數組;
$this->items["services"] = /var/www/laravel/config/services.php返回的數組;
$this->items["session"] = /var/www/laravel/config/session.php返回的數組;
$this->items["view"] = /var/www/laravel/config/view.php返回的數組;

假如有這樣的文件（/var/www/laravel/config/xx/yy/zz/file.php），返回["a"=>"hello,world!"]數組
將得到：$this->items["xx"]["yy"]["zz"]["file"] = ["a"=>"hello,world!"];
獲取方式： $config->get("xx.yy.zz.file.a", $default)，直接返回"hello,world!";

設置應用的錯誤異常等處理事件(IlluminateFoundationBootstrapHandleExceptions)

public function bootstrap(Application $app)
{
    $this->app = $app;

    error_reporting(-1);

    set_error_handler([$this, "handleError"]);

    set_exception_handler([$this, "handleException"]);

    register_shutdown_function([$this, "handleShutdown"]);

    if (! $app->environment("testing")) {
        ini_set("display_errors", "Off");
    }
}
public function handleError($level, $message, $file = "", $line = 0, $context = [])
{
    if (error_reporting() & $level) {
        throw new ErrorException($message, 0, $level, $file, $line);
    }
}
public function handleException($e)
{
    if (! $e instanceof Exception) {
        $e = new FatalThrowableError($e);
    }

    $this->getExceptionHandler()->report($e);

    if ($this->app->runningInConsole()) {
        $this->renderForConsole($e);
    } else {
        $this->renderHttpResponse($e);
    }
}
// 核心代碼，獲取的AppExceptionsHandle對象
protected function getExceptionHandler()
{
    // make時將會直接調用$this->bindings["IlluminateContractsDebugExceptionHandler"]["concrete"](此代碼位于/var/www/laravel/bootstrap/app.php，應用對象化后，直接注入到服務容器的幾個單例)，返回AppExceptionsHandle對象，并將此對象注入到服務容器[參考]
    return $this->app->make(ExceptionHandler::class);
}
protected function renderHttpResponse(Exception $e)
{
    $this->getExceptionHandler()->render($this->app["request"], $e)->send();
}
// AppExceptionsHandle
public function render($request, Exception $e)
{
    $e = $this->prepareException($e);

    if ($e instanceof HttpResponseException) {
        return $e->getResponse();
    } elseif ($e instanceof AuthenticationException) {
        return $this->unauthenticated($request, $e);
    } elseif ($e instanceof ValidationException) {
        return $this->convertValidationExceptionToResponse($e, $request);
    }

    return $this->prepareResponse($request, $e);
}
protected function renderHttpException(HttpException $e)
{
    $status = $e->getStatusCode();

    view()->replaceNamespace("errors", [
        resource_path("views/errors"),
        __DIR__."/views",
    ]);

    if (view()->exists("errors::{$status}")) {
        return response()->view("errors::{$status}", ["exception" => $e], $status, $e->getHeaders());
    } else {
        return $this->convertExceptionToResponse($e);
    }
}
public function handleShutdown()
{
    if (! is_null($error = error_get_last()) && $this->isFatal($error["type"])) {
        $this->handleException($this->fatalExceptionFromError($error, 0));
    }
}

根據配置項設置應用的 Facades(IlluminateFoundationBootstrapRegisterFacades)

public function bootstrap(Application $app)
{
    Facade::clearResolvedInstances();

    Facade::setFacadeApplication($app);
    // 將配置文件/var/www/laravel/config/app.php返回數組的鍵為aliases的值賦給IlluminateFoundationAliasLoader的aliases屬性，并進行注冊
    AliasLoader::getInstance($app->make("config")->get("app.aliases", []))->register();
}
public static function clearResolvedInstances()
{
    static::$resolvedInstance = [];
}
public static function setFacadeApplication($app)
{
    static::$app = $app;
}

IlluminateFoundationAliasLoader
public static function getInstance(array $aliases = [])
{
    if (is_null(static::$instance)) {
        return static::$instance = new static($aliases);
    }

    $aliases = array_merge(static::$instance->getAliases(), $aliases);

    static::$instance->setAliases($aliases);

    return static::$instance;
}
private function __construct($aliases)
{
    $this->aliases = $aliases;
}
public function getAliases()
{
    return $this->aliases;
}
public function setAliases(array $aliases)
{
    $this->aliases = $aliases;
}
public function register()
{
    if (! $this->registered) {
        $this->prependToLoaderStack();

        $this->registered = true;
    }
}
protected function prependToLoaderStack()
{
    // 將$this->load注冊到自動加載器的最前面，失敗時拋異常
    spl_autoload_register([$this, "load"], true, true);
}
public function load($alias)
{
    // $facadeNamespace = "Facades"，估計是框架內部使用的，以后再看吧
    if (static::$facadeNamespace && strpos($alias, static::$facadeNamespace) === 0) {
        $this->loadFacade($alias);

        return true;
    }

    if (isset($this->aliases[$alias])) {
        return class_alias($this->aliases[$alias], $alias);
    }
}

Facade的本質

實際上是通過$app->make("config")->get("app.aliases", [])取出config/app.php文件里面的aliases數組并實例化AliasLoader，再將AliasLoader->load方法放到spl自動加載器最前面，最后通過class_alias($this->aliases[$alias], $alias)。當調用Cache::Method時，會觸發Facdes的__callStatic魔術方法，此方法會調用相應對象里面的方法。

注入配置項的服務提供者(IlluminateFoundationBootstrapRegisterProviders)

public function bootstrap(Application $app)
{
    $app->registerConfiguredProviders();
}
public function registerConfiguredProviders()
{
    (new ProviderRepository($this, new Filesystem, $this->getCachedServicesPath()))
                ->load($this->config["app.providers"]);
}
public function getCachedServicesPath()
{
    return $this->bootstrapPath()."/cache/services.php";
}

// 先取services緩存文件，再對IlluminateFoundationProviderRepository進行實例化，隨后加載系統配置文件(./config/app.php)里面的providers數組
(new ProviderRepository($this, new Filesystem, $this->getCachedServicesPath()))
                ->load($this->config["app.providers"])
public function __construct(ApplicationContract $app, Filesystem $files, $manifestPath)
{
    $this->app = $app;
    $this->files = $files;
    $this->manifestPath = $manifestPath;
}
public function load(array $providers)
{
    $manifest = $this->loadManifest();

    if ($this->shouldRecompile($manifest, $providers)) {
        $manifest = $this->compileManifest($providers);
    }

    foreach ($manifest["when"] as $provider => $events) {
        $this->registerLoadEvents($provider, $events);
    }

    foreach ($manifest["eager"] as $provider) {
        // 直接注冊服務(將直接調用服務的register方法)
        $this->app->register($provider);
    }

    $this->app->addDeferredServices($manifest["deferred"]);
}
public function loadManifest()
{
    if ($this->files->exists($this->manifestPath)) {
        $manifest = $this->files->getRequire($this->manifestPath);

        if ($manifest) {
            return array_merge(["when" => []], $manifest);
        }
    }
}
public function shouldRecompile($manifest, $providers)
{
    return is_null($manifest) || $manifest["providers"] != $providers;
}
protected function compileManifest($providers)
{
    $manifest = $this->freshManifest($providers);

    foreach ($providers as $provider) {
        $instance = $this->createProvider($provider);
        // 延遲加載的服務
        if ($instance->isDeferred()) {
            foreach ($instance->provides() as $service) {
                $manifest["deferred"][$service] = $provider;
            }
            // 注冊延遲的事件
            $manifest["when"][$provider] = $instance->when();
        }
        // 即時加載的服務
        else {
            $manifest["eager"][] = $provider;
        }
    }

    return $this->writeManifest($manifest);
}
protected function freshManifest(array $providers)
{
    return ["providers" => $providers, "eager" => [], "deferred" => []];
}
public function createProvider($provider)
{
    return new $provider($this->app);
}
public function isDeferred()
{
    return $this->defer;
}
public function writeManifest($manifest)
{
    if (! is_writable(dirname($this->manifestPath))) {
        throw new Exception("The bootstrap/cache directory must be present and writable.");
    }

    $this->files->put(
        $this->manifestPath, " []], $manifest);
}
protected function registerLoadEvents($provider, array $events)
{
    if (count($events) < 1) {
        return;
    }

    $this->app->make("events")->listen($events, function () use ($provider) {
        $this->app->register($provider);
    });
}
public function addDeferredServices(array $services)
{
    $this->deferredServices = array_merge($this->deferredServices, $services);
}

大致流程

通過/var/www/laravel/bootstrap/cache/services.php等實例化IlluminateFoundationProviderRepository，并加載$this->config["app.providers"]數組。實例化app.providers各服務提供者，根據其defer屬性將服務進行分類(延遲服務|即時服務)，從而得到一個$manifest數組(格式如services.php，延遲處理：deferred=>注冊延遲的服務，以后再進行調用；when=>注冊延遲的事件；即時處理：eager=>直接進行注冊調用等)，并重新寫入到services.php，然后根據此文件進行相應的處理。

啟動服務提供者的boot方法等操作(IlluminateFoundationBootstrapBootProviders)

public function bootstrap(Application $app)
{
    $app->boot();
}
public function boot()
{
    if ($this->booted) {
        return;
    }
    // 可以通過應用的booting方法來注冊服務啟動前的事件監聽者
    $this->fireAppCallbacks($this->bootingCallbacks);
    // 嘗試調用所有的服務提供者的boot方法
    array_walk($this->serviceProviders, function ($p) {
        $this->bootProvider($p);
    });

    $this->booted = true;
    // 可以通過應用的booted方法來注冊服務啟動后的事件監聽者，若已經啟用了，則直接出發事件
    $this->fireAppCallbacks($this->bootedCallbacks);
}
protected function fireAppCallbacks(array $callbacks)
{
    foreach ($callbacks as $callback) {
        call_user_func($callback, $this);
    }
}
protected function bootProvider(ServiceProvider $provider)
{
    if (method_exists($provider, "boot")) {
        return $this->call([$provider, "boot"]);
    }
}