PHP - Manual: 相对类类型
2025-10-31
这些类型声明只能在类中使用。
   The value must be an instanceof the same class as the one
   in which the type declaration is used.
  
   值必须是 instanceof 使用了类型声明的父级类。
  
   static is a return-only type which requires that the
   value returned must be an instanceof the same class as the one
   the method is called in.
   自 PHP 8.0.0 起可用。
  
官方地址:https://www.php.net/manual/en/language.types.relative-class-types.php