$classObject = new MyClass();
foreach ($classObject as $item) {}<?php
class MyClass
{
    public $public = 'значение 1';
    protected $protected = 'защищённая переменная';
    private $private   = 'закрытая переменная';
    public function iterateAll() {
       foreach ($this as $key => $value) {
           print "$key => $value\n";
       }
    }
}
$class = new MyClass();
$class->iterateAll();