<?php
class A
{
    protected $bar = array('baz');

    function bar()
    {
        array_pop($this->bar);
        $vars = get_object_vars($this);
        $this->bar[] = array('buz');
        print_r($vars);
    }

    function foo() {
        array_pop($this->bar);
        $dummy = &$this->bar;
        $vars = get_object_vars($this);
        $this->bar[] = array('buz');
        print_r($vars);
    }
}

(new A())->bar();
(new A())->foo();
?>