中间件实现

<?php
// 框架核心应用层
$application = function ($name) {
    echo "this is a {$name} application\n";
};

// 前置校验中间件
$auth = function ($handler) {
    return function ($name) use ($handler) {
        echo "{$name} need a auth middleware\n";
        return $handler($name);
    };
};

// 前置过滤中间件
$filter = function ($handler) {
    return function ($name) use ($handler) {
        echo "{$name} need a filter middleware\n";
        return $handler($name);
    };
};

// 后置日志中间件
$log = function ($handler) {
    return function ($name) use ($handler) {
        $return = $handler($name);
        echo "{$name} need a log middleware\n";
        return $return;
    };
};

// 中间件栈
$stack = [];

// 打包
function pack_middleware($handler, $stack)
{
    foreach (array_reverse($stack) as $key => $middleware) {
        $handler = $middleware($handler);
    }
    return $handler;
}

// 注册中间件
// 这里用的都是全局中间件，实际应用时还能够为指定路由注册局部中间件
$stack['log'] = $log;
$stack['filter'] = $filter;
$stack['auth'] = $auth;

$run = pack_middleware($application, $stack);
print_r($run);
$run('Laravle');