php中变量引用&不可与global共同使用

　　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() 
    {
        $this->name = _get(); // null
        mlog("success, and model->name = {$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 variables
    global $CI; //non-boject
    //return $CI->load->name(); // 500
    return $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   
    }