How to sign a request in Masterpass?

Question

PHP

Hello everyone, the task is to connect Masterpass. So far, I only have an understanding that I will use the PHP OAuth module.
So far there is this piece:

try {
  $oauth = new OAuth('conskey',
        'conssec',
        OAUTH_SIG_METHOD_RSASHA1);
    $oauth->enableDebug();

        $requestTokenSigned = $oauth->generateSignature('POST','https://testwallet.masterpass.ru/mpapiv2/GetRequestToken', [
      'MerchantName' => 'MercantName',
            'Phone' => 'PhoneNumber'
        ]);

  $accessInfo = $oauth->getRequestToken($requestTokenSigned);

    if(!empty($accessInfo)) {
        print_r($accessInfo);
    } else {
        print "Failed fetching request token, response was: " . $oauth->getLastResponse();
    }
} catch (OAuthException $e) {
  print_r($e->getMessage());
}

I get an exception "Segmentation fault (core dumped)", which is interesting, the generateSignature() method is not highlighted in my IDE, although it is listed as public in the documentation.
Maybe I'm not doing everything right and everything is generally needed differently, I will be grateful if you direct me.