Make calls programmatically through Skype

I have a web application that I'm looking to integrate with Skype (or any similar service) in the following way: Be able to programmatically (by clicking a button on the web page) call a specified phone number. And when the person picks up the phone, have them hear an automatated voice message I have pre-recorded. But there will be a few variables that will be read by a "computer voice" (text-to-speech), such as a person's name or date. I don't expect you to develop a new text-to-speech synthesizer, but to find an existing product we can use. The current web application is written in PHP and on a Linux server. The Skype "plugin" doesn't necessarily have to be either as long as I can interface with it. Please give an expected time frame, budget, and the technologies you plan on using.