简单DI

<?php
class DI
{
    private $container;

    public function set($key, $obj, ...$args)
    {
        $this->container[$key] = [
            'obj'    => $obj,
            'params' => $args
        ];
    }

    public function delete($key)
    {
        unset($this->container[$key]);
    }

    public function clear()
    {
        $this->container = [];
    }

    public function get($key)
    {
        if (isset($this->container[$key])) {
            $res = $this->container[$key];
            if (is_object($res['obj']) && !is_callable($res['obj'])) {
                return $res['obj'];
            } elseif (is_callable($res['obj'])) {
                $this->container[$key]['obj'] = call_user_func($res['obj']);
                return $this->container[$key]['obj'];
            } elseif (is_string($res['obj']) && class_exists($res['obj'])) {
                $reflection                   = new \ReflectionClass ($res['obj']);
                $ins                          = $reflection->newInstanceArgs($res['params']);
                $this->container[$key]['obj'] = $ins;
                return $this->container[$key]['obj'];
            } else {
                return $res['obj'];
            }
        } else {
            return null;
        }
    }
}

class Test1
{
    public function show()
    {
        echo "hello World \n";
    }
}

class Test2
{
    public function __construct($name)
    {
        echo '我是参数' . $name . PHP_EOL;
    }

    function show()
    {
        echo "我是test2";
    }
}

class Test4
{
    public function show()
    {
        echo "test4";
    }
}

$DI = new DI();

$DI->set('name', 'zhangsan');

echo "注入字符串" . $DI->get('name') . PHP_EOL;

$test1 = new Test1();

$DI->set('test1', $test1);

echo "获取对象" . $DI->get('test1')->show() . PHP_EOL;

$DI->set('test2', Test2::class, 'zhangsa');

$DI->get('test2')->show();

$DI->set('test3', function () {
    return new Test4();
});

$DI->get('test3')->show();