[php classes and objects] Final keyword

1.类，不能被继承。
2.方法，不能被子类覆盖。
3.属性,常量，不能被定义为 Final

Example #1 Final 方法示例<?phpclass BaseClass {
   public function test() {
       echo "BaseClass::test() called\n";
   }   final public function moreTesting() {
       echo "BaseClass::moreTesting() called\n";
   }
}class ChildClass extends BaseClass {
   public function moreTesting() {
       echo "ChildClass::moreTesting() called\n";
   }
}// Results in Fatal error: Cannot override final method BaseClass::moreTesting()?>

Example #2 Final 类示例<?phpfinal class BaseClass {
   public function test() {
       echo "BaseClass::test() called\n";
   }   // 这里无论你是否将方法声明为final，都没有关系
   final public function moreTesting() {
       echo "BaseClass::moreTesting() called\n";
   }
}class ChildClass extends BaseClass {}// 产生 Fatal error: Class ChildClass may not inherit from final class (BaseClass)?>