Asterisk Attended Transfer within PhpAGI

Hello, We need to add a functionality to our IVR which is based on Asterisk V 13.14.0 / PhpAGI. Os is Debian 8, database is MySql 5, Php is also 5. Simple functionality: - Inbound call accepted (client who needs support) - IVR (PhpAGI) says "welcome" - Call is forwarded to 1st level agent (already done by DIAL command) - 1st level agent takes call, but finds out he need to ask 2nd level support colleague - 1st level does a click on web application list of destinations/numbers, the server (e.g. php cron) sends a transfer command for a connect of the 1st level agent to 2nd level support to asterisk. Important: it has to be an attended transfer, the 1st and 2nd level agents have to talk while the caller has to be parked. - then option a: 2nd level hangs up, 1st level and client can go on, or - option b: client will be connected to 2nd level ...which should be a typical inbound support situation. Our ideas to initiate the transfer so far: by mysql (asterisk polls, but we are in the thread of the caller, so we have no control of the call to the 1st level agent) or phpagi-asmanager (our php based server can send commands) or anything else. As we understand, the first connect to the 1st level agent by DIAL can't be controlled on the called side. All agent phone numbers have to be taken dynamically from a database, for this reason we use phpagi. Agent status (free/inactive) is also set in the database. We expect our partner to develop an example script and structure where we have a solution for all steps and can simulate our abvone explainde process. This solution we adapt and integrate then into our existing application. We won't change to another script language, database etc. We also don't want to install additional services to our IVR. For all questions and missing information write me. Thank you for your input.