Get the value of a specific header
Note that if the header has more than one value, an array will be returned.
string $key:
string|array|null The header value or null if it is not set
public function getHeader($key) {
$key = strtolower($key);
if (isset($this->headers[$key])) {
return $this->headers[$key][1];
}
else {
return null;
}
}