<?php

    $a = array('123' => '123');
    $o1 = (object)$a;
    $o2 = new stdClass;
    $o2->{'123'} = '123'; // setting property is OK

    echo "123 go: ".$o1->{'123'}."\n"; // error!
    echo "123 go: ".$o2->{'123'}."\n"; // works... WTF?