public function addVaryHttpHeader($header)
{
$vary = $this->getHttpHeader('Vary');
$currentHeaders = array();
if ($vary) {
$currentHeaders = preg_split('/\\s*,\\s*/', $vary);
}
$header = $this->normalizeHeaderName($header);
if (!in_array($header, $currentHeaders)) {
$currentHeaders[] = $header;
$this->setHttpHeader('Vary', implode(', ', $currentHeaders));
}
}