PHP as a web browser?

Is it possible to have PHP act like a web browser, accept cookies and post data (for login)? I'm not sure exactly where to start- I know you can use fopen/file to retrieve url's but I'm not too sure about the other steps. I would like to write and run such a php script as a cron job and have it do something like log into my web-based email account, retrieve emails, process them, save them locally, and then delete them on the server. Thanks for any help. David