How to get JSON.stringify into PHP with json_decode without AJAX?

Question

Say, I have something like this

function submitform() {
    var data = JSON.stringify({
        "userdata": $('#user_data').val()
    })
    $('<input type="hidden" name="json"/>').val(data).appendTo('#myform');
    $("#myform").submit();
}

Now on the Server side, I've tried:

json_decode($_POST['json']);
json_decode($_POST['json'], true);
json_decode(htmlspecialchars_decode($_POST['json']), true);

All of these return NULL value when I do a var_dump on the page.

I am not submitting the form via ajax, and I do not want to use application/json to submit the form because there are other fields in the form that need to be submitted the normal form submission way.

How can I do this?? Just need to send json to php on form submission.

Under what event are you calling submitform()? What's the action attribute set to on the form element? Also note that your method of appending the user_id to the URL is really not secure in any way. — Rory McCrossan
– Rory McCrossan, Commented Jan 27, 2016 at 17:14
What is the method used on your form? I know, it could be obvious, but if its not filled in you will need to look inside $_GET... — somethinghere
– somethinghere, Commented Jan 27, 2016 at 17:14
There you go. That's magic quotes working. Do a stripslashes() and it will work. — dkellner
– dkellner, Commented Jan 27, 2016 at 17:23

dkellner · Accepted Answer · 2016-01-27 17:40:05Z

2

Probably the magic quotes screw up your JSON string and PHP doesn't recognize it anymore. Use stripslashes() before you hand it over to json_decode():

$a = json_decode(stripslashes($_POST['json']));
var_dump($a);

answered Jan 27, 2016 at 17:40

dkellner

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3 Comments

Solomon Closson Over a year ago

Is there a way to check for magic quotes or will stripslashes() in order to know whether to use it or not, or will it work either way?

Solomon Closson Over a year ago

Is it needed to be known you think? Before doing stripslashes? Like I wouldn't want this script to get screwed up on different server with different magic quotes set.

dkellner Over a year ago

Normally you can do a strip() safely every time. But if your string contains intentional backslashes (? does it? very unlikely), stripslashes() will remove them. Which is a mistake, of course. Also, consider base64 if you want to receive EVERYTHING without all the mess :)

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