Remote Print Screen Output

I don't know if this is possible, but I would like to use PHP and the server it is installed on to visit a URL and save a screenshot of the page at certain intervals using a cron job.

Is this at all possible?

I'm not a unix guy, but I would look for a command line screen capture tool you could call from the cron job. I don't see the use for php unless you have alot of sites to capture.. then the database access would help i guess.