ThinkPHP5.1x的中间件，其核心还是闭包函数的应用，来实现“责任链”模式：

 

模拟代码：

     ';    }}//中间件class Before1 {    public function handle($request, Closure $next) {        echo 'before1
';  //业务逻辑，注意前置与后置中间件业务逻辑代码的位置        return $next($request);    }}//中间件class Before2 {    public function handle($request, Closure $next) {        echo 'before2
';        return $next($request);    }}//中间件class After1 {    public function handle($request, Closure $next) {        $response = $next($request);        echo 'after1
'; //业务逻辑，注意前置与后置中间件业务逻辑代码的位置        return $response;    }}//中间件class After2 {    public function handle($request, Closure $next) {        $response = $next($request);        echo 'after2
';        return $response;    }}class Middleware {    public static $queue;  //中间件队列    public static function init() {                //模拟的中间件，数量任意添加        self::$queue[] = [[After1::class,  'handle'], null];        self::$queue[] = [[After2::class,  'handle'], null];        self::$queue[] = [[Before1::class, 'handle'], null];        self::$queue[] = [[Before2::class, 'handle'], null];         //模拟的控制器        self::$queue[] = [[Controller::class,  'index'], null];    }        //调用中间件    public static function dispatch($request) {        call_user_func(self::resolve(), $request);    }        //返回闭包函数    public static function resolve(){        return function($request){            $middleware = array_shift(self::$queue);            if ($middleware != null) {                list($call, $param) = $middleware;                call_user_func_array($call, [$request, self::resolve()]);  //执行中间件            }        };    }}$request = "模拟的request对象";Middleware::init();Middleware::dispatch($request);