src/ResourceServer.php
public function determineAccessToken($headerOnly = FALSE)
    {
		switch ($headerOnly){
			case FALSE:
				$accessToken = $this->requestHandler->getParam($this->tokenKey);
				if ($accessToken !== null){
					break;
				}
			case TRUE:
				$tokenType = $this->getTokenType();
				if (strrpos(get_class($tokenType),"Bearer") !== FALSE){
					$accessToken = $tokenType->determineAccessTokenInHeader($this->requestHandler,$this->authHeader);
				}else{
					$accessToken = $tokenType->determineAccessTokenInHeader($this->requestHandler);
				}
				break;
		}

        if (empty($accessToken)) {
            throw new InvalidRequestException('access token');
        }

        return $accessToken;
    }
public function determineAccessToken($headerOnly = FALSE)
    {
		switch ($headerOnly){
			case FALSE:
				$accessToken = $this->requestHandler->getParam($this->tokenKey);
				if ($accessToken !== null){
					break;
				}
			case TRUE:
				$tokenType = $this->getTokenType();
				if (strrpos(get_class($tokenType),"Bearer") !== FALSE){
					$accessToken = $tokenType->determineAccessTokenInHeader($this->requestHandler,$this->authHeader);
				}else{
					$accessToken = $tokenType->determineAccessTokenInHeader($this->requestHandler);
				}
				break;
		}

        if (empty($accessToken)) {
            throw new InvalidRequestException('access token');
        }

        return $accessToken;
    }
Reads in the access token from the headers

@param bool $headerOnly Limit Access Token to Authorization header

@throws \OAuth2\Server\Exception\InvalidRequestException Thrown if there is no access token presented

@return string