SplEnum 为何不直接定义为：final class SplEnum，而在其内个方法添加final ？？？？

[twomiao]

疑问：这样就可以删除方法上面“多余的final”，还是仅仅某些方法打算继承，才这样写？？？？？？？
`final class SplEnum
{
private $val = null;
private $name = null;

public function __construct($val)
{
    $list = self::getConstants();
    //禁止重复值
    if (count($list) != count(array_unique($list))) {
        $class = static::class;
        throw new \Exception("class : {$class} define duplicate value");
    }
    $this->val = $val;
    $this->name = self::isValidValue($val);
    if($this->name === false){
        throw new \Exception("invalid value");
    }
}

public function getName():string
{
    return $this->name;
}

public function getValue()
{
    return $this->val;
}

}`