了解 CodeIgniter 中的load_class

>im试图理解CodeIgniter中的框架结构，我刚刚开始并提出了这个小误解。

所以有人可以在以下立场下帮助我：-

1-为什么他们使用引用来传递类的实例...我的意思是为什么不只是一个简单的变量？

2-为什么该函数将类的名称存储在数组中而不是"字符串变量"中（请不要判断我的php术语是最糟糕的）..... ？！

static $_classes = array();
                   ^^^^^^^ this cloud be just ("") or am i missing something

这是函数，所以你不会去寻找它。

function &load_class($class, $directory = 'libraries', $prefix = 'CI_')
    {
        static $_classes = array();
        // Does the class exist?  If so, we're done...
        if (isset($_classes[$class]))
        {
            return $_classes[$class];
        }
        $name = FALSE;
        // Look for the class first in the local application/libraries folder
        // then in the native system/libraries folder
        foreach (array(APPPATH, BASEPATH) as $path)
        {
            if (file_exists($path.$directory.'/'.$class.'.php'))
            {
                $name = $prefix.$class;
                if (class_exists($name) === FALSE)
                {
                    require($path.$directory.'/'.$class.'.php');
                }
                break;
            }
        }
        // Is the request a class extension?  If so we load it too
        if (file_exists(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php'))
        {
            $name = config_item('subclass_prefix').$class;
            if (class_exists($name) === FALSE)
            {
                require(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php');
            }
        }
        // Did we find the class?
        if ($name === FALSE)
        {
            // Note: We use exit() rather then show_error() in order to avoid a
            // self-referencing loop with the Excptions class
            exit('Unable to locate the specified class: '.$class.'.php');
        }
        // Keep track of what we just loaded
        is_loaded($class);
        $_classes[$class] = new $name();
        return $_classes[$class];
    }