Example PHP JWT token generation using SHA512 encryption

jwt.php

<?php

function base64url_encode($data) {
  return rtrim(strtr(base64_encode($data), '+/', '-_'), '=');
}

function generateJwtToken($secret) {
  $header = base64_encode('{
    "typ": "JWT",
    "alg": "HS512"
  }');
  $payload = base64_encode('{
    "iat": '. time() .'
  }');
  $signature = base64url_encode(hash_hmac('sha512', $header .'.'. $payload , $secret, true));
  return $header .'.'. $payload .'.'. $signature;
}

$token = generateJwtToken('secretToken');
echo $token;