Yes, I think that the caching on my site is a bit too aggressive: I'm only using an Amazon Micro instance, so I mostly rely on CloudFlair to deliver my content fast, but it does mean I sometimes need to clear the cache before comments show up.
After the script displays your customer ids, it then has some arbitrary sample code that create a campaign in the first account; if you run the code again, you'll get an error message because it will try and create another campaign with the same name. I'll modify it to work like the official sample code to add a timestamp so the name will always be unique.
After getting a sandbox account set up, you should check out the PHP sample code that comes with the client library because it should have examples of most of the operations you're likely to want to perform.