// Using Guzzle
$client = new Client();
$request = new Request('get', 'https://my-exchange-url.com');
$user_name = 'user_name';
$password = 'password';
$target_name = 'target_name';
$host_name = 'host_name';

$encoding_converter = new MbstringEncodingConverter();
$random_byte_generator = new NativeRandomByteGenerator();
$hasher_factory = HasherFactory::createWithDetectedSupportedAlgorithms();

$negotiate_message_encoder = new NegotiateMessageEncoder($encoding_converter);
$challenge_message_decoder = new ChallengeMessageDecoder();

$keyed_hasher_factory = KeyedHasherFactory::createWithDetectedSupportedAlgorithms();

$nt1_hasher = new NtV1Hasher($hasher_factory, $encoding_converter);
$nt2_hasher = new NtV2Hasher($nt1_hasher, $keyed_hasher_factory, $encoding_converter);

$authenticate_message_encoder = new NtlmV2AuthenticateMessageEncoder(
    $encoding_converter,
    $nt2_hasher,
    $random_byte_generator,
    $keyed_hasher_factory
);

$negotiate_message = $negotiate_message_encoder->encode(
    $target_name,
    $host_name
);

// Send negotiate message
$request->setHeader('Authorization', sprintf('NTLM %s', base64_encode($negotiate_message)));
$response = $client->send($request);

// Decode returned challenge message
$authenticate_headers = $response->getHeaderAsArray('WWW-Authenticate');
foreach ($authenticate_headers as $header_string) {
    $ntlm_matches = preg_match('/NTLM( (.*))?/', $header_string, $ntlm_header);

    if (0 < $ntlm_matches && isset($ntlm_header[2])) {
        $raw_server_challenge = base64_decode($ntlm_header[2]);
        break;
    }
}
$server_challenge = $challenge_message_decoder->decode($raw_server_challenge);

$authenticate_message = $authenticate_message_encoder->encode(
    $user_name,
    $target_name,
    $host_name,
    new Password($password),
    $server_challenge
);

// Send authenticate message
$request->setHeader('Authorization', sprintf('NTLM %s', base64_encode($authenticate_message)));
$client->send($request);