PHP命名空间例子

1、文件a.php 

<?php 
class Ball{

    function play(){
        echo "I am playing football";
    }
}

?>

2.文件b.php

<?php 
class Ball{

    function play(){
        echo "I am playing basketball";
    }
}

?>

3.文件 index.php

<?php 
require("a.php");
require("b.php");
$ball = new Ball();
$ball->play();
?>

提示错误： Cannot redeclare class Ball in。。。。因为累Ball在文件a和b中都重复定义了。

如果a文件跟改为:

<?php
namespace football;
class Ball{
    function  play(){
        echo "I am playing football";
    }
}

?>

b 文件

<?php
namespace basketball;
class Ball{

    function play(){
        echo "I am playing basketball";
    }
}

?>

index.php

<?php 
require("a.php");
require("b.php");

use football\ball as a_ball;
use basketball\ball as b_ball;

$a_ball = new a_ball();
$a_ball->play();

$b_ball = new b_ball();
$b_ball->play();
?>