/**
* Parse the expiration time from a series of HTTP headers.
*
* @param array $headers
* @return int|NULL
* Expiration tme as seconds since epoch, or NULL if not cacheable.
*/
public static function parseExpiration($headers)
{
$headers = CRM_Utils_Array::rekey($headers, function ($k, $v) {
return strtolower($k);
});
if (!empty($headers['cache-control'])) {
$cc = self::parseCacheControl($headers['cache-control']);
if ($cc['max-age'] && is_numeric($cc['max-age'])) {
return CRM_Utils_Time::getTimeRaw() + $cc['max-age'];
}
}
return NULL;
}
