JSFiddle - React, Tailwind, and code Playground
HTML
<html>
<form action="" method="post">
<input type="radio" name="paid" value="0" checked="checked"/>No<br>
<input type="radio" name="paid" value="1"/>Yes
</form>
<?php
$paid = $_POST['paid'];
echo $paid;
?>
</html>
JavaScript
$('input[name=paid]').change(function(){
$('form').submit();
});