function b64($data) {return strtr(base64_encode($data), '+/', '-_');}
$priv_key = '-----BEGIN RSA PRIVATE KEY-----...-----END RSA PRIVATE KEY-----';
$addri = rand(1,9999);
$pkeyid = openssl_get_privatekey($priv_key);
$data = $u . "
php,$addri

";
openssl_sign($data, $signature, $pkeyid);
$key = b64($signature);
$kvitok = b64($data.$key);