json - Get a PHP object property that is a number

I'm trying to get a property from JSON data decoded into a PHP object. It's just a YouTube data API request that returns a video object that has a content object liks so;

[content] => stdClass Object
                (
                    [5] => https://www.youtube.com/v/r4ihwfQipfo?version=3&f=videos&app=youtube_gdata
                    [1] => rtsp://v4.cache7.c.youtube.com/CiILENy73wIaGQn6pSL0waGIrxMYDSANFEgGUgZ2aWRlb3MM/0/0/0/video.3gp
                    [6] => rtsp://v6.cache3.c.youtube.com/CiILENy73wIaGQn6pSL0waGIrxMYESARFEgGUgZ2aWRlb3MM/0/0/0/video.3gp
                )

Doing

$object->content->5

Throws "unexpected T_DNUMBER" - which makes perfect sense. But how do I get the value of a property that is a number?

I'm sure I should know this. Thanks in advance.

Answer

This should work:

$object->content->{'5'}