PHP Helper functions for Safe Base64 URL encode

base64_url_safe.php

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

function base64url_decode($data) { 
  return base64_decode(str_pad(strtr($data, '-_', '+/'), strlen($data) % 4, '=', STR_PAD_RIGHT)); 
} 
?>

• Encode: https://github.com/firebase/php-jwt/blob/feb0e820b8436873675fd3aca04f3728eb2185cb/src/JWT.php#L350
• Decode: https://github.com/firebase/php-jwt/blob/feb0e820b8436873675fd3aca04f3728eb2185cb/src/JWT.php#L333