I'd like to be able to include a tag when making a spot request via PHP. When creating on-demand instances, you can create the instance, then use it's instance to issue the following:
array('Key' => 'Name', 'Value' => 'MyTestMachine'),
the answer is that you cannot assign a tag until the instance is actually created. In order to tag this I have used a listener daemon to watch new instances and tag them once they've started.