Zimbra Self-Registration / User Creation Page

I need someone experienced or at least aware of Zimbra to create a script that will handle someone registering for an e-mail account. It will check if the account exists, if it doesn't it will let the user register, if it does exist it will ask the user to pick a new username. We are going to launch a small e-mail service provider and need someone experienced in either JAVA or PHP/SOAP to work with Zimbra API