The documentation for the transfer() function under the WebAPI suggests support for the on "Connect" event, allowing the callee of the transfer() function to interact with the platform before the caller is connected.
Are you able to provide an example of how this could be coded, using the PHP library?
The suggested use is for call screening, providing the opportunity to reject a call before it's transferred through, but I don't understand how you could build logic if there were an array such as:
$options = array("on" => array("event" => "connect", <logic to screen calls goes here?>));
Are you able to provide some more information on this?