guzzle 中间件原理

<?php

#闭包链式调用

$handle = function ($method) {
    echo $method, PHP_EOL;
    return 'done';
};

$stack = [];

array_push($stack, [function ($callable, $msg) use($handle) {
    return function () use ($callable, $msg) {
        echo '闭包 1', PHP_EOL;
        return $callable($msg);
    };
}, 'one']);

array_push($stack, [function ($callable, $msg) use($handle) {
    return function () use ($callable, $msg) {
        echo '闭包 2', PHP_EOL;
        return $callable($msg);
    };
}, 'two']);

$prev = $handle;
foreach (array_reverse($stack) as $k => $fn) {
    $prev = $fn[0]($prev, $fn[1]);
}

echo $prev();

echo '----------------', PHP_EOL;

$prev = $handle;
foreach ($stack as $k => $fn) {
    $prev = $fn[0]($prev, $fn[1]);
}

echo $prev();