php require_once()引入文件后，后面的代码无法执行

<?php

if(!defined('CORE_ROOT')) exit;

require_once CORE_ROOT.'include/mailconfig.inc.php'; //此处引入后

class smtp {

var $host;

var $user;

var $pass;

var $port;

var $sock;

var $from;

function smtp($host = '', $user = '', $pass = '', $from = '', $port = 25) {

if(empty($host)) {

global $smtphosts;

echo 'aaaaa';

var_dump($smtphosts);die; //此处无法执行显示

if(empty($smtphosts)) return false;

排查结果为:

$smtphosts = array(

'host'= 'localhost',

'user'= '1017314129@qq.com',

'pass'= 'flzx6qc',

'from'= '',

);