Storing and retrieving an array in a PHP cookie

Question

I'm looking to store some data from some 'virtual' index cards. Each card has a front and a back, and the user can store multiple cards. Each side will have data on it.

I ----------------- I I CARD 1 FRONT I I------------------I
I --------------- I I CARD 1 BACK I I-----------------I
I ----------------- I I CARD 2 FRONT I I------------------I
I --------------- I I CARD 2 BACK I I-----------------I

OK, my diagrams got messed up a bit. But you get the message. :)

Imagine it from the diagrams above. I'd like to store each card's data (front and back) in a cookie, as an array (maybe), and then be able to pull each value back and insert it where applicable (on a different page).

At the same time, bear in mind that the user can make as many cards as they like. I can't use POST or GET functions. The array bit is debatable, if you can think of an easier way of storing this data in a cookie, let me know. Please note: don't suggest storing in a database, as it won't be convenient for the project. :)

Answer 1

Use json_encode / json_decode to get / set arrays in cookies.

Test array

$cardArray=array(
    'CARD 1'=>array('FRONT I', 'BACK I'),
    'CARD 2'=>array('FRONT 2', 'BACK 2')
);

convert and write the cookie

$json = json_encode($cardArray);
setcookie('cards', $json);

the saved string looks like this

{"CARD 1":["FRONT I","BACK I"],"CARD 2":["FRONT 2","BACK 2"]}

get the cookie back

$cookie = $_COOKIE['cards'];
$cookie = stripslashes($cookie);
$savedCardArray = json_decode($cookie, true);

show the restored array

echo '<pre>';
print_r($savedCardArray);
echo '</pre>';

outputs

Array
(
    [CARD 1] => Array
        (
            [0] => FRONT I
            [1] => BACK I
        )

    [CARD 2] => Array
        (
            [0] => FRONT 2
            [1] => BACK 2
        )

)

---

Edit
If you wonder about stripslashes, it is because the string saved actually is

{"CARD 1":["FRONT I","BACK I"],"CARD 2":["FRONT 2","BACK 2"]}

setcookie adds before quoutes to escape them. If you not get rid of those, json_decode will fail.

---

Edit II

To add a new card to the cookie

1. load the array as above
2. $savedCardArray['CARD XX']=array('FRONT XX', 'BACK XX');
3. save the array as above, but now of course $savedCardArray and not $cardArray.