[DarkChris]

примерно так

var calendarListener:Object = new Object();
var ref = this;
calendarListener.change = function(evt_obj:Object) {
   var selDate : Date = evt_obj.target.selectedDate;
   var sendDate : String = selDate.getFullYear().toString()+"-"+selDate.getMonth().toString()+"-"+selDate.getDate().toString();
   ref.sendToPHP(sendDate);
};
calendar.addEventListener("change",calendarListener);
function sendToPHP(s:String){
	trace(s);
}