Use the Date class
http://www.adobe.com/livedocs/flash/9.0/ActionScriptLangRefV3/
Particularly the parse() property , but you should also be able to use a PHP timestamp and get the Date class to return a String
//value returned from PHP
var timestamp:Number = 1234670090;
var date:Date = new Date(timestamp);
var date2:Date = new Date();
var time:String = date2.parse('07:00:00');
// trace( date ) or trace( time ) should give you a String
//with the format Sat Nov 30 15:20:00 GMT-0800 1974
You can use the date variable's properties to return the year , month , day , hours, minutes etc...