YII2中actions的作用是什么

<?php
 
//注意这里的命名空间，要跟你的目录对应
namespace app\common;
 
use yii\base\Action;
 
//我们需要继承yii\base\Action类
class TestAction extends Action {
 
    //这里面的三个参数的值是通过控制器actions中配置而来的
    public $param1 = null;
    public $param2 = null;
    public $param3 = null;
 
    //实现run方法
    public function run() {
        echo "test run param1: {$this->param1} param2: {$this->param2} param3: {$this->param3}";
    }
}

<?php
 
namespace app\controllers;
 
use YII;
use yii\web\Controller;
 
class IndexController extends Controller
{
    //actions的作用主要是共用功能相同的方法
    public function actions()
    {
        return [
            &#39;test&#39; => [
                &#39;class&#39; => &#39;app\common\TestAction&#39;,
                &#39;param1&#39; => &#39;hello&#39;,
                &#39;param2&#39; => &#39;world&#39;,
                &#39;param3&#39; => &#39;!!!&#39;,
            ],
        ];
    }
}