Encoding with JS base64 and deciding with php base64_decode

Question

I'm sending users to a new link which has a value that is encoded with Javascript's btoa, however, on the PHP side, when I decode it and echo the value out, the value that is echoed out is "undefined"

    $("#btn-print-bonus").click(function(){
        var id = btoa(id);
        window.open('/pdf/?type=bonus&id='+id+'&name='+fullname+'');
    });

php file

$id = base64_decode($_GET["id"]);
echo $id;

Where does fullname and id come from? If you open the browser developer tools and set a breakpoint on the click handler, you might be able to see what the argument to window.open will be. — Phil Cooper
– Phil Cooper, Commented Dec 20, 2016 at 9:02
PHP will never generate the undefined keyword by itself because it has no special meaning in the language. I'm pretty sure you have a literal undefined encoded in Base64. — Álvaro González
– Álvaro González, Commented Dec 20, 2016 at 9:05

Jaromanda X · Accepted Answer · 2016-12-20 09:01:42Z

1

here's the problem - var id = btoa(id);

var id will "mask" any var named id outside of that click callback, so in effect you are doing

var id = undefined;
id = btoa(id);

Which results in id=dW5kZWZpbmVk passed to php - check in the developer tools network tab and see if I'm right

dW5kZWZpbmVk is the string "undefined" base64 encoded - btoa coerces the given argument to a string

answered Dec 20, 2016 at 9:01

Jaromanda X

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