$level = rand(1, 3);

class board
{
    public $power = 1;
    protected $top = 'admin';

    public function process($level)
    {
        if ($level <= $this->power) {
            echo "删帖";
        } else {
            $top = new $this->top;
            $top->process($level);
        }
    }
}

class admin
{
    public $power = 2;
    protected $top = 'police';

    public function process($level)
    {
        if ($level <= $this->power) {
            echo "封号";
        } else {
            $top = new $this->top;
            $top->process($level);
        }
    }
}

class police
{
    public $power = 2;
    protected $top = null;

    public function process($level)
    {
        echo "抓起来";
    }
}

$judge = new board();
$judge->process($level);