/**
* Sends an expires header.
* @param $mExpires The expires header to send. Can be one of the following:
* • A DateInterval object
* • A date interval spec in the form of Pxx (http://en.wikipedia.org/wiki/Iso8601#Durations) which will be added to today’s date
* • A UNIX timestamp as an integer
* • A string to be parsed into a date using strtotime
* • A DateTime object
* • A Cache object (which will be asked about the expiresTimestamp)
* • `true` to expire in a year (the maxiumum permitted by RFC2616)
* • `false` to mark as already expired (and to force re-evaluation)
*/
public static function sendExpires($mTimestamp)
{
if (self::$EXPIRES_SENT) {
return;
}
if ($mTimestamp instanceof Cache) {
$mTimestamp = $mTimestamp->getStrategy()->expiresTimestamp($mTimestamp);
}
if ($mTimestamp === true) {
$mTimestamp = 'P1Y';
}
if (is_string($mTimestamp) && substr($mTimestamp, 0, 1) === 'P') {
$mTimestamp = new DateInterval($mTimestamp);
}
if (is_string($mTimestamp)) {
$mTimestamp = strtotime($mTimestamp);
}
if ($mTimestamp === null) {
return;
}
if ($mTimestamp instanceof DateInterval) {
$oDate = new DateTime('now', new DateTimeZone('UTC'));
$mTimestamp = $oDate->add($mTimestamp);
} else {
if ($mTimestamp instanceof DateTime) {
$mTimestamp = clone $mTimestamp;
$mTimestamp->setTimezone(new DateTimeZone('UTC'));
} else {
if (is_int($mTimestamp)) {
$mTimestamp = new DateTime("@{$mTimestamp}");
}
}
}
// Format for output
if ($mTimestamp === false) {
$mTimestamp = 0;
} else {
$mTimestamp = $mTimestamp->format(self::DATE_RFC2616);
}
header('Expires: ' . $mTimestamp);
self::$EXPIRES_SENT = true;
}