问题来源，新公司debug。
程序中代码大致如下
class Ci {private static $instance = NULL; ???????public $name = ‘hello‘; ???????public $load = null; ???????public function __construct() ???????{ ???????self::$instance = &$this; ???????$this->load = new Load; ???????mlog(self::$instance, __LINE__);//other code ....$this->name = ‘my name‘; ???????}public static function &getInstance(){return self::$instance;} ???} ???class My extends Ci{ ???????public function __construct() ???????{parent::__construct();$this->model = new Model; ???????} ???} ???class Model {public function __construct() {$this->name = _get(); // nullmlog("success, and model->name = {$this->name}", __LINE__);} } class Load {public $name = ‘I am Load class‘;public function getName() {return $this->name;} } ???$CI =& get_instance(); ???// mlog($CI->name); //hello ???// mlog($CI->load->getName()); //I am Load class ???mlog($CI, __LINE__); $CI = new My; mlog($CI, __LINE__); function _get() {//call static variablesglobal $CI; //non-boject//return $CI->load->name(); // 500return $CI->name; //notice } function &get_instance() {return Ci::getInstance(); } function mlog($content, $line = __LINE__,$display = true) {$next_line = "<br />";if (php_sapi_name() === ‘cli‘) { $init = ‘‘; $next_line = "\n";} if ($display) { echo $init; echo "in line: $line" . $next_line; print_r($content); echo $next_line;} }相信朋友们可以看出来，这是CI框架中的一部分，开发者为了封装方法所以在helper中使用如下代码
<?php ???$CI =& get_instance(); ???function demo() ????{ ????????global $CI; ????????//return $CI->mehton; ?????????//notice ????????//return $CI->class->method;//500 ??????}服务器直接报了500。通过我第一部分的代码与注释，应该可以得出以下结论：在function的scope中global $ref是拿不到该引用的，php手册中也有说明，详情请看。干啥都不能不细心啊，好好学习基础^_^
php中变量引用&不可与global共同使用
原文地址：http://www.cnblogs.com/jixingke/p/7573042.html