Question

When the user submits an HTML form, I want to disable the form while the server is processing it. I don’t want the user to type any additional text, nor do I want them to rapidly tap the submit button to send multiple requests. I tried doing this with Prototype JS:

$('formId').observe(
    'submit',
    function(event) {
        Event.element(event).disable();
    }
);

The form correctly gets disabled, but on the server side, I error_log out $_POST and find that it is completely empty. This problem only occurs when the form is disabled upon submission.

Answer 1

If you disable the form, I think it will not submit / post your fields, because it’ll be diabled, What I do in that cases is disable the submit button, not the whole form.

$('formId').observe(
    'submit',
    function(event) {
        $$("input[type='submit']").each(function(v) {v.disabled = true;})
    }
);

Take a look to this How can I unobtrusively disable submit buttons with Javascript and Prototype?

UPDATE:

But disabling the submit button is not enough. People can hit the
enter key on a text input to submit the form. Using the submit button
is not the only way to submit a form

Then you can make a combination with this answer https://stackoverflow.com/a/9693667/1078487

var already_submitted = false;

$('formId').observe(
    'submit',
    function(e) {
        // disable input
        $$("input[type='submit']").each(function(v) {v.disabled = true;})
        if ( already_submitted ) {
            new Event(e).stop();
            return false;
        } else {
            already_submitted = true;
        }
    }
);