When submitting a GET form, the query string is removed from the action URL

Admin 1
Viewed 417422

Consider this form:

<form action="http://www.blabla.com?a=1&b=2" method="GET">
    <input type="hidden" name="c" value="3" /> 
</form>

When submitting this GET form, the parameters a and b are disappearing.
Is there a reason for that?
Is there a way of avoiding this behaviour?

http-get forms html
12 Answers

Isn't that what hidden parameters are for to start with...?

<form action="http://www.example.com" method="GET">
  <input type="hidden" name="a" value="1" /> 
  <input type="hidden" name="b" value="2" /> 
  <input type="hidden" name="c" value="3" /> 
  <input type="submit" /> 
</form>

I wouldn't count on any browser retaining any existing query string in the action URL.

As the specifications (RFC1866, page 46; HTML 4.x section 17.13.3) state:

If the method is "get" and the action is an HTTP URI, the user agent takes the value of action, appends a `?' to it, then appends the form data set, encoded using the "application/x-www-form-urlencoded" content type.

Maybe one could percent-encode the action-URL to embed the question mark and the parameters, and then cross one's fingers to hope all browsers would leave that URL as it (and validate that the server understands it too). But I'd never rely on that.

By the way: it's not different for non-hidden form fields. For POST the action URL could hold a query string though.

user_842370

In HTML5, this is per-spec behaviour.

See Association of controls and forms - Form submission algorithm.

Look at "4.10.22.3 Form submission algorithm", step 17. In the case of a GET form to an http/s URI with a query string:

Let destination be a new URL that is equal to the action except that its <query> component is replaced by query (adding a U+003F QUESTION MARK character (?) if appropriate).

So, your browser will trash the existing "?..." part of your URI and replace it with a new one based on your form.

In HTML 4.01, the spec produces invalid URIs - most browsers didn't actually do this though...

See Forms - Processing form data, step four - the URI will have a ? appended, even if it already contains one.

user_6154710

You should include the two items (a and b) as hidden input elements as well as C.

user_397220

When the original query has array, for php:

foreach (explode("\n", http_build_query($query, '', "\n")) as $keyValue) {
    [$key, $value] = explode('=', $keyValue, 2);
    $key = htmlspecialchars(urldecode($key), ENT_COMPAT | ENT_HTML5);
    $value = htmlspecialchars(urldecode($value), ENT_COMPAT | ENT_HTML5);
    echo '<input type="hidden" name="' . $key . '" value="' . $value . '"' . "/>\n";
}
user_71039910

To answer your first question yes the browser does that and the reason is that the browser does not care about existing parameters in the action URL so it removes them completely

and to prevent this from happening use this JavaScript function that I wrote using jQuery in:

function addQueryStringAsHidden(form){
    if (form.attr("action") === undefined){
        throw "form does not have action attribute"
    }

    let url = form.attr("action");
    if (url.includes("?") === false) return false;
    
    let index = url.indexOf("?");
    let action = url.slice(0, index)
    let params = url.slice(index);
    url = new URLSearchParams(params);
    for (param of url.keys()){
        let paramValue = url.get(param);
        let attrObject = {"type":"hidden", "name":param, "value":paramValue};
        let hidden = $("<input>").attr(attrObject);
        form.append(hidden);
    }
    form.attr("action", action)
}
user_133927250
Related