<?php
class wc
{
    public function __construct($who)
    {
        echo "{$who}准备去上厕所了";
    }

    public function go()
    {
        echo "1.跑出了教室";
        return $this;
    }

    public function action($ss)
    {
        echo $ss . "2.到了厕所，开始尿尿";
        return $this;
    }

    public function back()
    {
        echo "3.尿尿结束，回到教室";
        return $this;
    }
}

$xm = new wc("小明");
$xm->go()->action("<br>")->back();