php中类的static变量使用

<?php
#访问静态变量
#类外部: 类名::$类变量名
#类内部: 娄名::$类变量名或self::$类变量名
class Char{
    public static $number = 0;
    public $name;
    
    function __construct($what){
        $this->name = $what;
    }
    function Join(){
        self::$number++;
        echo self::$number," Is :",$this->name,"<br />";
    }
    
}

$test = range('a','z');
foreach($test as $values){
    $what = new Char($values);
    $what->Join();
}