id_user | password      | nombre |     email
-------------------------------------------------
     1  | $2y$10$pDweWy | pedro  | pedro@mail.com
     2  | $2y$10$l43VL1 | juan   | juan@mail.com
     3  | $2y$10$TJdiWI | diego  | diego@mail.com

id_user |          password              | nombre |     email
-------------------------------------------------------------------
     1  | FPbDMzL3hoUkM4ME9aZW56eWF1abcd | pedro  | pedro@mail.com
     2  | ptTXJCTndPOE9ucElQa2ZtSXg2Ly5o | juan   | juan@mail.com
     3  | BkQjN1QkdINWFsS3hQUHA2QTU2QmVr | diego  | diego@mail.com

<?php

$firma=getenv('TOKEN_SECRET');

$info_relevante=[
    'id_user'=>1,
    'nombre'=>'pedro',
    'email'=> 'pedro@mail.com',
    'expiracion'=>1531484696103
];

$parte_central = base64_encode(json_encode($info_relevante));

eyJpZF91c2VyIjoxLCJub21icmUiOiJwZWRybyIsImVtYWlsIjoicGVkcm9AbWFpbC5jb20iLCJleHBpcmFjaW9uIjoxNTMxNDg0Njk2MTAzfQ==

$token = funcion_firma_jwt($parte_central, $firma);
// forma del token: qwertyx.<parte_central>.asdfg_zxcvb