Convert date string to UTC time with PHP

I have the following date string

$date="Sat Apr 30 2011 18:47:47 GMT+0900 (Tokyo)"

I want to convert it to UTC time

$timestamp_UN开发者_如何转开发IX = strtotime($date);
echo date("Y-m-d\TH:i:s\Z",$timestamp_UNIX);

Why do I got

2011-04-30T11:47:47Z
and not
2011-04-30T09:47:47Z

The problem is that you code does not automatically echo UTC. It echos the timestamp in whatever your default timezone is set to. This is done via date_default_timezone_set() at runtime or via the configuration setting date.timezone in your php.ini.

The modern way would be to use the DateTime and the DateTimeZone classes.

$d = new DateTime('Sat Apr 30 2011 18:47:47 GMT+0900 (Tokyo)');
print_r($d);
$d->setTimezone(new DateTimeZone('UTC'));
print_r($d);

prints

DateTime Object
(
    [date] => 2011-04-30 18:47:47
    [timezone_type] => 1
    [timezone] => +09:00
)
DateTime Object
(
    [date] => 2011-04-30 09:47:47
    [timezone_type] => 3
    [timezone] => UTC
)

You should use gmdate() instead of date() (or you could check the DateTime and DateTimeZone classes in PHP 5.2 / 5.3)