In PHP -- Video File Conversion

In PHP -- I need to be able to offer the service of downloading a video file in whatever format the customer wants. For example; if the video file wanted is in MP4 but the customer prefers to convert it to WMV I would like to offer that option by just clicking on the WMV button. There are probably 15 different video format types plus compressed files like Zip and Rar. This must be integrated in PHP and will have to work with my developers for integration.