mail merge simulation on php/mysql web site

I'm looking to providing a mail merge simulation on my web site to prevent users from needing to have MS Word (mail merge) or similar program. I would like my web site to provide the following: -gui? like that of Word / Mail Merge -users can create text for mailer and save these letters to database -users can create text for envelopes and save to database -mapped fields are automatically populated? based on records from the database.? this is the main functionality of mail merge in which a user can map fields of a database (in this case mysql) to fields of the letter & envelope which will be automatically populated.