public function sendHeaders()
{
if (headers_sent()) {
throw new \LogicException('Headers already send');
}
header("HTTP/1.1 {$this->getHttpCode()}");
header("Content-Type:{$this->getContentType()}; charset={$this->getCharset()}");
header("Content-Language: {$this->getLanguage()}");
header("X-Response-Date: " . Header::toGmtDate());
$modified = $this->getModified();
Header::modified($modified);
$cacheTime = $this->getTimeToCache();
if ($cacheTime > 0) {
Header::cache($cacheTime);
} elseif ($cacheTime < 0) {
Header::noCache();
}
header("ETag: {$this->getEtag()}");
}