how to create JSON API for web and mobile app for Ejabberd chat server?

Questions 1: Which is best XMPP client for ejabberd chat server?

Detail : I am totally new to add chat into my web and mobile application. I need to help to understand, how can I proceed with. I am php developer. I want implement chat in my web application. how can I integrate database with my web application database. I know ejabberd has own database, where it save all information about users.

I want to know, how can I proceed with.