Custom Web Script

Hi. I need a simple web script (preferably in PHP) embedded in a webpage that submits a username and a password to a form on another website every 5 minutes, regadless of the outcome - which will be that the username and password do not match. Still, every time it does this, the same combination of username and password should be used. I need to be able to change the combination and the frequency of the submits manually if I so desire. The form should look something like this: Username: someusername Password: somepassword Frequency in seconds: 300 The webform that this gets sent to is always the same and on a static address so I don't need to be able to change that. Thank you.