PHPMailer\PHPMailer\PHPMailer::DKIM_Sign PHP Метод

    public function DKIM_Sign($signHeader)
    {
        if (!defined('PKCS7_TEXT')) {
            if ($this->exceptions) {
                throw new Exception($this->lang('extension_missing') . 'openssl');
            }
            return '';
        }
        $privKeyStr = file_get_contents($this->DKIM_private);
        if ('' != $this->DKIM_passphrase) {
            $privKey = openssl_pkey_get_private($privKeyStr, $this->DKIM_passphrase);
        } else {
            $privKey = openssl_pkey_get_private($privKeyStr);
        }
        if (openssl_sign($signHeader, $signature, $privKey, 'sha256WithRSAEncryption')) {
            openssl_pkey_free($privKey);
            return base64_encode($signature);
        }
        openssl_pkey_free($privKey);
        return '';
    }