PHP script to sync a db bi directionally

Hi, We need a php script written to do 2 tasks; 1) Get the data which has got updated after a particular time and send it in a particular JSON format 2) Php script which we can send data which has got updated from the mobile client to the server and the server db. Let me explain this in more details; Scenario 1; The user will click a button, and a http request will come to your PHP page. The request will have last_updated_time, this can be 0, if it's the first time or some value as milliseconds. If it's 0, then the php script will get data from all the tables and create the JSON structure we want. If the last_updated_time is not 0, then php script will see which records have got added, changed or removed, after the time which was sent from the client and get those data and respond as per the JSON structure we have defined. Scenario 2; We need to have a php script which we can send a json (predefined structure) so that when received those data can be added to the server db. Please do let me know the cost of it; We will provide the mysql tables for the server and the json structures. Regards,