php命名空间报错

<?php

namespace Article;

const PATH = '/article';

function getCommentTotal() {

    return 100;

}

class Comment { }

namespace MessageBoard;

const PATH = '/message_board';

function getCommentTotal() {

    return 300;

}

class Comment { }

//调用当前空间的常量、函数和类

echo PATH; ///message_board

echo getCommentTotal(); //300

$comment = new Comment();

//调用Article空间的常量、函数和类

echo \Article\PATH; ///article

echo \Article\getCommentTotal(); //100

$article_comment = new \Article\Comment();

?>

<?php

namespace Article;

const PATH = '/article';

function getCommentTotal() {

    return 100;

}

class Comment { }

namespace MessageBoard;

const PATH = '/message_board';

function getCommentTotal() {

    return 300;

}

class Comment { }

//调用当前空间的常量、函数和类

echo PATH; ///message_board

echo getCommentTotal(); //300

$comment = new Comment();

//调用Article空间的常量、函数和类

echo \Article\PATH; ///article

echo \Article\getCommentTotal(); //100

$article_comment = new \Article\Comment();

?>