| protected getCacheControlHeader ( ) : string | ||
| 리턴 | string | Either the value of the header or NULL if it shall be omitted |
protected function getCacheControlHeader()
{
$cacheControl = '';
foreach ($this->cacheDirectives as $cacheDirective) {
$cacheControl .= $cacheDirective !== '' ? $cacheDirective . ', ' : '';
}
$cacheControl = trim($cacheControl, ' ,');
return $cacheControl === '' ? null : $cacheControl;
}