SAML2\Assertion::addAuthnStatement PHP Method

    private function addAuthnStatement(\DOMElement $root)
    {
        if ($this->authnInstant === null || $this->authnContextClassRef === null && $this->authnContextDecl === null && $this->authnContextDeclRef === null) {
            /* No authentication context or AuthnInstant => no authentication statement. */
            return;
        }
        $document = $root->ownerDocument;
        $authnStatementEl = $document->createElementNS(Constants::NS_SAML, 'saml:AuthnStatement');
        $root->appendChild($authnStatementEl);
        $authnStatementEl->setAttribute('AuthnInstant', gmdate('Y-m-d\\TH:i:s\\Z', $this->authnInstant));
        if ($this->sessionNotOnOrAfter !== null) {
            $authnStatementEl->setAttribute('SessionNotOnOrAfter', gmdate('Y-m-d\\TH:i:s\\Z', $this->sessionNotOnOrAfter));
        }
        if ($this->sessionIndex !== null) {
            $authnStatementEl->setAttribute('SessionIndex', $this->sessionIndex);
        }
        $authnContextEl = $document->createElementNS(Constants::NS_SAML, 'saml:AuthnContext');
        $authnStatementEl->appendChild($authnContextEl);
        if (!empty($this->authnContextClassRef)) {
            Utils::addString($authnContextEl, Constants::NS_SAML, 'saml:AuthnContextClassRef', $this->authnContextClassRef);
        }
        if (!empty($this->authnContextDecl)) {
            $this->authnContextDecl->toXML($authnContextEl);
        }
        if (!empty($this->authnContextDeclRef)) {
            Utils::addString($authnContextEl, Constants::NS_SAML, 'saml:AuthnContextDeclRef', $this->authnContextDeclRef);
        }
        Utils::addStrings($authnContextEl, Constants::NS_SAML, 'saml:AuthenticatingAuthority', false, $this->AuthenticatingAuthority);
    }