#include<iostream>
using namespace std;
class Box{
private:
    int l,w;
public:
    void set(){
        l=0; w=0;
    }
　　//此处重载的是set()函数
    void set(int ll){
        l=ll; w=0;
    }
    void set(int ll,int ww){
        l=ll; w=ww;
    }

    void display(){
        cout<<"L="<<l<<";";
        cout<<"W="<<w<<endl;
    }
};
int main()
{
    Box box_1,box_2,box_3;
    box_1.set();
    cout<<"box_1:\n";
    box_1.display();

    box_2.set(5);
    cout<<"box_2:\n";
    box_2.display();

    box_3.set(7,9);
    cout<<"box_3:\n";
    box_3.display();
}

<?php
	class Student{
		public function display(){
			echo "I am a student! <br>";
			echo "I haven't graduate <br>";
		}
	}

	class Graduate extends Student{
		public function display(){
			//要想实现重载，则子类当中需要重载的函数名必须与父类当中此函数的函数名相同
			//此处以display()为例。
			echo "I was a student before! <br>";
			echo "but I have graduated! <br>";
		}
	}

	$stu=new Student();
	$stu->display();

	$gra=new Graduate();
	$gra->display();	
?>