private function processContentLength()
{
$length = strlen($this->content());
if (!$this->headers->has('Content-Length') || $this->headers->fetch('Content-Length') != $length) {
$this->headers->write('Content-Length', $length);
}
}
/**
* Checks if a cookie exists.
*
* @param string $key
*
* @return bool
*/
public function has(string $key) : bool
{
return $this->collection->has($key);
}