How do I display tokens in a block using PHP code?

You could try token_replace

token_replace($text, array $data = array(), array $options = array())

Parameters

$text: A string potentially containing replaceable tokens.

$data: (optional) An array of keyed objects. For simple replacement scenarios 'node', 'user', and others are common keys, with an accompanying node or user object being the value. Some token types, like 'site', do not require any explicit information from $data and can be replaced even if it is empty.

$options: (optional) A keyed array of settings and flags to control the token replacement process. Supported options are:

I dont recommend using PHP in a block for many reasons.

I would recommend you to use proper implementation of hook_block_view and hook_block_info to do you custom PHP codes in there.