php类知识 self $this都只能在当前类中使用

<?php
class mycoach
{
    public $name="陈培昌";
    CONST hisage =22;
    public static $earnfor =2789;
    public static $address = "北京市朝阳区三里屯soho北武堂";
    private $favorite = "喜欢丁大锅";
    public function __construct()
    {
        echo "{$this->name}到目前为止，为馆里卖出的装备价值".mycoach::$earnfor."元".PHP_EOL;
    }
    public static function workingaddr()
    {
        echo self::$address.PHP_EOL;
    }
}
$cpc = new mycoach();
$cpc->workingaddr();
?>