讀 Slim 框架代碼（1）

<p>一直都想找個PHP 的 web 框架的代碼來讀讀，好學習一下 web 框架都是怎麼寫的。可是通常的 PHP 框架好像都比較傲複雜。以前在 Mysapce 實習的時候用過一套本身寫的很是簡單的 MVC 框架，只是很薄的包了一層，把 Model，View 和 Controller 分開，我本身平時寫 PHP 應用也是用這種方法寫的。憑着記憶，把當時用的那套東西重現了一下（<a href="https://github.com/ljie-PI/php-mini-framework">github</a>）。</p>

<p>前幾天在 github 上發現<a href="https://github.com/codeguy/Slim">一個叫 Slim 的框架</a>，star 和 fork 數都不算少，也號稱很是輕量級，打算看一看它的源代碼。</p>

<h2>Hello World</h2>

<p>Slim Framework 的文檔第一個例子依然是 <a href="http://docs.slimframework.com/#Hello-World">Hello World</a>。先結合這個例子來看一看 Slim 的實現方法。</p>

<h3>第一步：建立 Slim 對象</h3>

<p>第一行代碼是：</p> ```php $app = new \Slim\Slim(); ``` <p>這一行代碼對應的 Slim 代碼以下：</p> <!--more--> ```php public function __construct(array $userSettings = array()) { // Setup IoC container $this->container = new \Slim\Helper\Set(); $this->container['settings'] = array_merge(static::getDefaultSettings(), $userSettings);

// Default environment
    $this->container->singleton('environment', function ($c) {
        return \Slim\Environment::getInstance();
    });

    // Default request
    $this->container->singleton('request', function ($c) {
        return new \Slim\Http\Request($c['environment']);
    });

    // Default response
    $this->container->singleton('response', function ($c) {
        return new \Slim\Http\Response();
    });

    // Default router
    $this->container->singleton('router', function ($c) {
        return new \Slim\Router();
    });

    // Default view
    $this->container->singleton('view', function ($c) {
        $viewClass = $c['settings']['view'];

        return ($viewClass instanceOf \Slim\View) ? $viewClass : new $viewClass;
    });

    // Default log writer
    $this->container->singleton('logWriter', function ($c) {
        $logWriter = $c['settings']['log.writer'];

        return is_object($logWriter) ? $logWriter : new \Slim\LogWriter($c['environment']['slim.errors']);
    });

    // Default log
    $this->container->singleton('log', function ($c) {
        $log = new \Slim\Log($c['logWriter']);
        $log->setEnabled($c['settings']['log.enabled']);
        $log->setLevel($c['settings']['log.level']);
        $env = $c['environment'];
        $env['slim.log'] = $log;

        return $log;
    });

    // Default mode
    $this->container['mode'] = function ($c) {
        $mode = $c['settings']['mode'];

        if (isset($_ENV['SLIM_MODE'])) {
            $mode = $_ENV['SLIM_MODE'];
        } else {
            $envMode = getenv('SLIM_MODE');
            if ($envMode !== false) {
                $mode = $envMode;
            }
        }

        return $mode;
    };

    // Define default middleware stack
    $this->middleware = array($this);
    $this->add(new \Slim\Middleware\Flash());
    $this->add(new \Slim\Middleware\MethodOverride());

    // Make default if first instance
    if (is_null(static::getInstance())) {
        $this->setName('default');
    }
}

<ul>
<li>Environment 對象中包含 REQUEST_METHO，REMOTE_ADD，REQUEST_URI 等各類 $_SERVER 環境變量</li>
<li>Request 對象中包含 REQUEST_METHOD，QUERY_STRING，HTTP_COOKIE 及各類 HTTP 請求頭內容</li>
<li>Response 對象包含響應狀態碼，header 及 body</li>
<li>Router 對象會解析請求的 URI 並關聯到對應的響應函數</li>
<li>View 對象能夠從 HTML 模板渲染頁面</li>
<li>LogWriter 和 Log 主要用來寫 log</li>
<li>Middle 數組是一串 middle，每一個請求過來會一次執行 Middle 對象的 call 方法</li>
</ul>

<h3>第二步：指定 route 和 callback</h3>

<p>這一步對應的代碼是：</p>

```php
    $app->get('/hello/:name', function ($name) {
        echo "Hello, $name";
    });

<p>此時會執行 Slim 對象的 mapRoute 方法，並關聯請求方法：</p>

public function get()
    {
        $args = func_get_args();

        return $this->mapRoute($args)->via(\Slim\Http\Request::METHOD_GET, \Slim\Http\Request::METHOD_HEAD);
    }

<p>在 mapRoute 方法中，會建立一個 Route 對象，將 「/hello/:name」 做爲 Route 對象的 pattern，將第二個參數（一個函數）做爲 Route 對象的 callable，並將這個 Route 對象加入到 Router 對象的 routes 數組中。</p> ```php protected function mapRoute($args) { $pattern = array_shift($args); $callable = array_pop($args); $route = new \Slim\Route($pattern, $callable); $this->router->map($route); if (count($args) > 0) { $route->setMiddleware($args); }

return $route;
}

<p>Route 對象的 via 方法</p>
```php
    public function via()
    {
        $args = func_get_args();
        $this->methods = array_merge($this->methods, $args);

        return $this;
    }

<h3>第三步：執行</h3>

<p>最後能夠執行代碼生成 reponse：</p> ```php $app->run(); ```

<p>這行代碼在 Slim.php 中對應：</p> ```php public function run() { set_error_handler(array('\Slim\Slim', 'handleErrors'));

//Apply final outer middleware layers
    if ($this->config('debug')) {
        //Apply pretty exceptions only in debug to avoid accidental information leakage in production
        $this->add(new \Slim\Middleware\PrettyExceptions());
    }

    //Invoke middleware and application stack
    $this->middleware[0]->call();

    //Fetch status, header, and body
    list($status, $headers, $body) = $this->response->finalize();

    // Serialize cookies (with optional encryption)
    \Slim\Http\Util::serializeCookies($headers, $this->response->cookies, $this->settings);

    //Send headers
    if (headers_sent() === false) {
        //Send status
        if (strpos(PHP_SAPI, 'cgi') === 0) {
            header(sprintf('Status: %s', \Slim\Http\Response::getMessageForCode($status)));
        } else {
            header(sprintf('HTTP/%s %s', $this->config('http.version'), \Slim\Http\Response::getMessageForCode($status)));
        }

        //Send headers
        foreach ($headers as $name => $value) {
            $hValues = explode("\n", $value);
            foreach ($hValues as $hVal) {
                header("$name: $hVal", false);
            }
        }
    }

    //Send body, but only if it isn't a HEAD request
    if (!$this->request->isHead()) {
        echo $body;
    }

    restore_error_handler();
}

<p>因爲 Slim 對象的最後一個 Middle 是自己，因此在執行完一堆 Middle 的 call 方法後會執行本身的 call 方法：</p>
```php
    public function call()
    {
        try {
            if (isset($this->environment['slim.flash'])) {
                $this->view()->setData('flash', $this->environment['slim.flash']);
            }
            $this->applyHook('slim.before');
            ob_start();
            $this->applyHook('slim.before.router');
            $dispatched = false;
            $matchedRoutes = $this->router->getMatchedRoutes($this->request->getMethod(), $this->request->getResourceUri());
            foreach ($matchedRoutes as $route) {
                try {
                    $this->applyHook('slim.before.dispatch');
                    $dispatched = $route->dispatch();
                    $this->applyHook('slim.after.dispatch');
                    if ($dispatched) {
                        break;
                    }
                } catch (\Slim\Exception\Pass $e) {
                    continue;
                }
            }
            if (!$dispatched) {
                $this->notFound();
            }
            $this->applyHook('slim.after.router');
            $this->stop();
        } catch (\Slim\Exception\Stop $e) {
            $this->response()->write(ob_get_clean());
            $this->applyHook('slim.after');
        } catch (\Exception $e) {
            if ($this->config('debug')) {
                throw $e;
            } else {
                try {
                    $this->error($e);
                } catch (\Slim\Exception\Stop $e) {
                    // Do nothing
                }
            }
        }
    }

<p>在 Router 的 getMatchedRoutes 方法中會針對請求的 URI，用正則表達式匹配是否有合適的 Route 對象，而且匹配出其中傳進來的參數</p> ```php public function getMatchedRoutes($httpMethod, $resourceUri, $reload = false) { if ($reload || is_null($this->matchedRoutes)) { $this->matchedRoutes = array(); foreach ($this->routes as $route) { if (!$route->supportsHttpMethod($httpMethod) && !$route->supportsHttpMethod("ANY")) { continue; }

if ($route->matches($resourceUri)) {
                $this->matchedRoutes[] = $route;
            }
        }
    }

    return $this->matchedRoutes;
}

```php
    public function matches($resourceUri)
    {
        //Convert URL params into regex patterns, construct a regex for this route, init params
        $patternAsRegex = preg_replace_callback(
            '#:([\w]+)\+?#',
            array($this, 'matchesCallback'),
            str_replace(')', ')?', (string) $this->pattern)
        );
        if (substr($this->pattern, -1) === '/') {
            $patternAsRegex .= '?';
        }

        //Cache URL params' names and values if this route matches the current HTTP request
        if (!preg_match('#^' . $patternAsRegex . '$#', $resourceUri, $paramValues)) {
            return false;
        }
        foreach ($this->paramNames as $name) {
            if (isset($paramValues[$name])) {
                if (isset($this->paramNamesPath[ $name ])) {
                    $this->params[$name] = explode('/', urldecode($paramValues[$name]));
                } else {
                    $this->params[$name] = urldecode($paramValues[$name]);
                }
            }
        }

        return true;
    }

<p>最後執行 Route 對象的 dispatch 方法，就是將匹配出來的參數傳到 callable 而後執行。</p>

public function dispatch()
    {
        foreach ($this->middleware as $mw) {
            call_user_func_array($mw, array($this));
        }

        $return = call_user_func_array($this->getCallable(), array_values($this->getParams()));
        return ($return === false)? false : true;
    }