Finding out the first possible booking date with php

Hello everybody, I am pretty much stuck with a problem and I was hoping to find some help here with you guys. A PHP Script with MySQL as DB has to find out the first possible booking period available. I can't figure out the logic behind and if there is a trick with PHP to do it. Following facts: - There can only be 3 bookings in the same time period - I want to find out the first period available - There should be a less as possible periods that are unbooked Example: Start End 1.12 14.12 4.12 18.12 5.12 19.12 In this example the first possible booking would be 14.12 - 28.12 as this is a time period where I can offer a place that holds a max of 3 bookings. My Problem now is how to pull this info and process it? Should I get all dates out of the DB and process them via PHP, or do a magical MYSQL Query (which by the way seems not to be possible in that case in my knowledge) ? Let's asume we go with PHP. Has somebody an idea how to form that kind of logic? Thank you for ANY help, merlin