public static function gc($maxlifetime)
{
$changed = false;
// check if the last update value exists and if not,
// set it to NOW, so the update process runs this time.
if (($nextupdate = XML::root()->getAttribute('next')) == "") {
XML::root()->setAttribute('next', $nextupdate = self::$_NOW);
$changed = true;
}
// proceed with the update only if its really time for it.
if (self::$_NOW >= (double) $nextupdate) {
$sess = XML::query('//session');
foreach ($sess as $s) {
// if the id has expired delete it.
if ($s->getAttribute('exp') <= self::$_NOW) {
$s->parentNode->removeChild($s);
@unlink(SESS . $s->getAttribute('id'));
$changed = true;
}
}
}
if ($changed) {
XML::save();
}
}