php - Failed to get an object property that containing ":protected"

I used the code below to get the object's property
_items:protected, but no
luck.

$obj =
            JSite::getMenu();
print_r($obj->_items:protected);

Object
output

JMenuSite
            Object
(

 [_items:protected] => Array

            (
 [101] => stdClass Object
 (
 [id] =>
            101
 [menutype] =>
            mainmenu

Anyone know
what wrong with my code? Thanks.

class="post-text" itemprop="text">

class="normal">Answer

You are trying to access a
protected property from outside the class.
A protected property can only be
accessed from within the class itself or classes that inherit from that
class.

Read up on OOP access
modifiers.