Form a list of booking web apps

Hi dear all, i would like to have a help on selecting a web app for simple half-hour appointments for my clients. Client would open my site and select one or more opened half-hour time slots. Ideally this app is made with following technologies: HTML, CSS, JQuery, mySQL, PHP App needs to be very simplistic. App has to be open for further in-house development. Thank you for taking your time to read this bid. Matko