Vacation Rental Availability Search

We maintain a vacation rental website for a client. The client uses an off-site booking calendar hosted by another company. They want to create a search feature that will allow visitors to input a desired date range for their visit, the number of guests and/or bedrooms they want and get a results screen that will list the properties that are available during that time that meet their bedroom or guest capacity request. The search will have to simultaneously query the off-site booking calendar (supports XML and JSON, cURL access) to get a list of the properties available, but the number of bedrooms and guest capacity is stored on our server's mySQL database. This will need to be seamless to the user with a simple input similar to that found on this page: [login to view URL] We'll need the code commented heavily so we can modify it over time as we add new units and remove others. We need the search data delivered as an array that will be plugged in to our existing site to display the search results.