A very simple, quick and dirty way of encoding and decoding URL Safe Base64 strings. Preview: http://sandbox.onlinephpfunctions.com/code/66abd8f5fd2b87bf91a5fba3e9d93dfd190cba09

URLSafeBase64.php

<?php
    echo "Encode BASE64: ----------\n";    
    $string = 'message:whatsup';
    $url = base64_url_encode($string);    
    echo "Encoded: ".$url."\n";
    
    echo "Now decode! --------------\n";    
    $decode = base64_url_decode($url);    
    $getClient = explode(":", $decode);
    foreach ($getClient as $str) {
        echo $str."\n";
    }
    
    function base64_url_encode($input) {
        return strtr(base64_encode($input), '+/=', '-_.');
    }    
    function base64_url_decode($input) {
        return base64_decode(strtr($input, '-_.', '+/='));
    }
?>