How to submit 0 if checkbox is unchecked and submit 1 if checkbox is checked in HTML

Simplest one, no javascript required, just put a hidden input before the checkbox:

<input type="hidden" name="check[0]" value="0" /><input type="checkbox" name="check[0]" value="1" />

Inputs need to have the same name. If the checkbox is checked then value 1 will be submitted, otherwise value 0 from the hidden input.

Your case javascript solution, no hidden inputs needed:

<script type="text/javascript">    // when page is ready    $(document).ready(function() {         // on form submit        $("#form").on('submit', function() {            // to each unchecked checkbox            $(this + 'input[type=checkbox]:not(:checked)').each(function () {                // set value 0 and check it                $(this).attr('checked', true).val(0);            });        })    })</script><form method="post" id="form">    <input type="checkbox" name="check[0]" value="1" />    <input type="checkbox" name="check[1]" value="1" />    <input type="submit" value="Save Changes" /></form>

PHP solution, no hidden inputs needed:

<?php    // if data is posted, set value to 1, else to 0    $check_0 = isset($_POST['check'][0]) ? 1 : 0;    $check_1 = isset($_POST['check'][1]) ? 1 : 0;?><form method="post">    <input type="checkbox" name="check[0]" value="1" />    <input type="checkbox" name="check[1]" value="1" />    <input type="submit" value="Save Changes" /></form>

EDIT: the javascript solution is not valid anymore as of jquery 1.6. Based on this, a more proper solution is the following:

<script type="text/javascript">    // when page is ready    $(document).ready(function() {         // on form submit        $("#form").on('submit', function() {            // to each unchecked checkbox            $(this).find('input[type=checkbox]:not(:checked)').prop('checked', true).val(0);        })    })</script><form method="post" id="form">    <input type="checkbox" name="check[0]" value="1" />    <input type="checkbox" name="check[1]" value="1" />    <input type="submit" value="Save Changes" /></form>

A better solution that solved this for me.

Problem: Both the hidden and the checked were sending to my server.

Solution:

if len(key) == 1 {  value = false} else {  value = true}

This way, if len(key) is 1 I know that only the hidden field was being send. Any other scenario means that the box is checked. Simple and easy.

Well I have a much more simple code that worked well for me:

<input type="checkbox" value="true" id="checkBox">

Then the JQuery code:

var checkBoxValue = $('#checkBox').is(':checked')?$('#checkBox').val():false

I used a ternary operator to set the value on checked and unchecked condition.