Codeigniter 升级php5.6提示Only varia

升级php5.6提示，Codeigniter 2.x项目提示

A PHP Error was encountered
Severity: Notice
Message: Only variable references should be returned by reference
Filename: core/Common.php
Line Number: 257

解决方法

进入system/core,修改Comm.php 257行

修改前

return $_config[0] =& $config;

修改后

$_config[0] =& $config; return $_config[0];