getRequestId() method is not able to capture header

[buzz8year]

public function getRequestId() {
        if (isset($this->headers['Request-Id'])) {
            return $this->headers['Request-Id'][0];
        }
        return null;
}

• given method is not able to capture header by key 'Request-Id' (reproduction is questionable)

• yet, using lowercased analogue 'request-id' returns expected...

• propose:

public function getRequestId() {
        if (isset($this->headers[strtolower('Request-Id')])) {
            return $this->headers[strtolower('Request-Id')][0];
        }
        return null;
}