php json_encode() is encoding in a way that JavaScript JSON.parse can't decode

Question

I am trying to work between PHP and Javascript, reading and writing the same cookie that contains a json value that I read into an array in both JS and PHP.

If I save the cookie having used json_encode() on my php array I find that the contents of the resulting cookie are all encoded, as if url encoded.

The problem is that when I try to then read that cookie and decode the JSON with

var existing_array = readCookie('cookie_name');
JSON.parse(existing_array)

I get a javascript error (such as Uncaught SyntaxError: Unexpected token %)

If I use a browser based cookie reader I can see that the array is easily readable when it is saved via javascript: ["644","636"].

However when the array is created in PHP via the json_encode() function the resulting content ends up as something like: %5B%22644%22%5D.

If this encoding wasn't happening i'm confident that the JS function could decode it. Has anyone else experienced this? I'm using PHP 5.5 on Windows 8 and the latest Chrome Browser.

Can't you just decode in JS? decodeURI( readCookie('...') ) — EvilZebra
– EvilZebra, Commented Apr 18, 2015 at 17:57
The contents in the cookie is URL encoded. Decode it first if you want to JSON.parse it properly. — N.B.
– N.B., Commented Apr 18, 2015 at 17:58

Álvaro González · Accepted Answer · 2015-04-20 14:17:33Z

Cookies need to be stuffed in HTTP headers so they get encoded for transmision:

setcookie('cookie_name', '["644","636"]');

... triggers:

Set-Cookie: cookie_name=%5B%22644%22%2C%22636%22%5D

... and the browser sends this back:

Cookie: cookie_name=%5B%22644%22%2C%22636%22%5D

Your readCookie() function should take care of decoding data properly but it seems it doesn't. If you want to fix it, you can take some ideas from e.g. the jquery-cookie plug-in:

function parseCookieValue(s) {
    if (s.indexOf('"') === 0) {
        // This is a quoted cookie as according to RFC2068, unescape...
        s = s.slice(1, -1).replace(/\\"/g, '"').replace(/\\\\/g, '\\');
    }

    try {
        // Replace server-side written pluses with spaces.
        // If we can't decode the cookie, ignore it, it's unusable.
        // If we can't parse the cookie, ignore it, it's unusable.
        s = decodeURIComponent(s.replace(pluses, ' '));
        return config.json ? JSON.parse(s) : s;
    } catch(e) {}
}

Please note the decodeURIComponent part.

AdamJones · Accepted Answer · 2015-04-22 13:19:52Z

4

Thank you @Evilzebra, it was simply adding decodeURIComponent at the start of the JS that resolved it.

decodeURIComponent(readCookie('cookie_name'));

edited Apr 22, 2015 at 13:19

answered Apr 18, 2015 at 19:47

AdamJones

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2 Comments

Álvaro González Over a year ago

Looks like a messy solution. Why use a readCookie() function that can't read a cookie properly?

Brien Crean Over a year ago

JSON.parse($.cookie(cookie_name')) seems like a better solution, reference stackoverflow.com/questions/18318545/…

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