OneLogin_Saml2_Settings::checkSPCerts PHP Method

    public function checkSPCerts()
    {
        $key = $this->getSPkey();
        $cert = $this->getSPcert();
        return !empty($key) && !empty($cert);
    }

 /**
  * Generates the Signature for a SAML Response
  *
  * @param string $samlResponse  The SAML Response
  * @param string $relayState    The RelayState
  * @param string $signAlgorithm Signature algorithm method
  *
  * @return string A base64 encoded signature
  *
  * @throws Exception
  * @throws OneLogin_Saml2_Error
  */
 public function buildResponseSignature($samlResponse, $relayState, $signAlgorithm = XMLSecurityKey::RSA_SHA1)
 {
     if (!$this->_settings->checkSPCerts()) {
         throw new OneLogin_Saml2_Error("Trying to sign the SAML Response but can't load the SP certs", OneLogin_Saml2_Error::SP_CERTS_NOT_FOUND);
     }
     $key = $this->_settings->getSPkey();
     $objKey = new XMLSecurityKey($signAlgorithm, array('type' => 'private'));
     $objKey->loadKey($key, false);
     $security = $this->_settings->getSecurityData();
     if ($security['lowercaseUrlencoding']) {
         $msg = 'SAMLResponse=' . rawurlencode($samlResponse);
         if (isset($relayState)) {
             $msg .= '&RelayState=' . rawurlencode($relayState);
         }
         $msg .= '&SigAlg=' . rawurlencode($signAlgorithm);
     } else {
         $msg = 'SAMLResponse=' . urlencode($samlResponse);
         if (isset($relayState)) {
             $msg .= '&RelayState=' . urlencode($relayState);
         }
         $msg .= '&SigAlg=' . urlencode($signAlgorithm);
     }
     $signature = $objKey->signData($msg);
     return base64_encode($signature);
 }