Can anyone suggest an easy method to convert date and time to different timezones in php?
An even simpler method looks like this:
date_default_timezone_set('Europe/London'); // your user's timezone
$my_datetime='2013-10-23 15:47:10';
echo date('Y-m-d H:i:s',strtotime("$my_datetime UTC"));
As described in the PHP manual, strtotime() accepts a timezone too, you just have to append it to your datetime.
I recommend you to store all your datetimes in UTC because that way you won't have problems with the daylight savings.