Whats wrong with DateTime object

Question

Can anyone tell what is wrong with the code.

$timezone = "Asia/Karachi"; 
$date = new DateTime($when_to_send, new DateTimeZone($timezone));
$date = $date->setTimezone(new DateTimeZone('GMT')); 
$when_to_send = $date->format('Y-m-d H:i:s');

error is: Call to a member function format() on a non-object

Answer 1

$date = $date->setTimezone(new DateTimeZone('GMT'));

Makes the $date variable null, you should just call it:

$date->setTimezone(new DateTimeZone('GMT'));

Answer 2

If you're not running at least PHP 5.3.0 (as written in the manual, which you surely read before asking, right?), setTimezone will return NULL instead of the modified DateTime. Are you running at least PHP 5.3.0?