you can create hypercubes that represent data from the qix engine. You can have a look at the help for understanding on how to create and read in .NetSDK.
Yes this is totally possible. I have done this using an extension and PHP5 .
You will be able to read data in qlik which comes from a hyper cube, then format the data into required Json format and use an ajax call to send data to your PHP file and post it to your database. I have tried posting it to MySQL Database.