keeping radio buttons checked after form submit - html

Question

I have two set of radio buttons in html form button and button1. I am using below code to
1.keep the default value checked (question1 for first set and answer2 for next set)
2.keep user radio button selection after the form submit
<div id="button_set1">
<input onClick="show_seq_lunid();" type="radio" name="button" value="Yes" <?php if(isset($_POST['button']) && $_POST['button'] == 'Yes') echo ' checked="checked"';?> checked /><label>question1</label>
<input onClick="show_list_lunid();" type="radio" name="button" value="No" <?php if(isset($_POST['button']) && $_POST['button'] == 'No') echo ' checked="checked"';?> /><label>answer1</label>
</div>
<div id="button_set2">
<input onClick="os_hpux();" type="radio" name="button1" value="Yes" <?php if(isset($_POST['button1']) && $_POST['button1'] == 'Yes') echo ' checked="checked"';?> /><label>question2</label>
<input onClick="os_others();" type="radio" name="button1" value="No" <?php if(isset($_POST['button1']) && $_POST['button1'] == 'No') echo ' checked="checked"';?> checked /><label>answer2</label>
</div>
Here if i use below code, the second radio button button1 is not sticking on to the user selection after form submit, it changing back to its default checked state.ie answer2. But the first set of radio buttons work fine.
If I remove the default checked option from the code, both radio buttons working fine after form submit. How can I keep the radio button checked after form submit while using checked default option for radios

Answer 1

So, the problem is you're setting the checked value twice upon form submission, resulting in selecting either the default value (from initial form state) or the value that has been submitted.
For this to work correctly, you'd need always use PHP to append the checked value to your radio elements, like this:
<div id="button_set1">
<input onClick="show_seq_lunid();" type="radio" name="button" value="Yes" <?php if(!isset($_POST['button']) || (isset($_POST['button']) && $_POST['button'] == 'Yes')) echo ' checked="checked"'?> /><label>question1</label>
<input onClick="show_list_lunid();" type="radio" name="button" value="No" <?php if(isset($_POST['button']) && $_POST['button'] == 'No') echo ' checked="checked"';?> /><label>answer1</label>
</div>
<div id="button_set2">
<input onClick="os_hpux();" type="radio" name="button1" value="Yes" <?php if(isset($_POST['button1']) && $_POST['button1'] == 'Yes') echo ' checked="checked"';?> /><label>question2</label>
<input onClick="os_others();" type="radio" name="button1" value="No" <?php if(!isset($_POST['button1']) || (isset($_POST['button1']) && $_POST['button1'] == 'No')) echo ' checked="checked"';?> /><label>answer2</label>
</div>
Here's a working preview: http://codepad.viper-7.com/rbInpX
Also, please note that you're using inline JavaScript notation which is normally discouraged to keep dynamic JS content separate and more manageable ;-)

Answer 2

I had a similar problem recently, but had a lot more radio buttons to deal with, so I thought I'd abstract away the value checking functionality into a method that also creates the radio button itself, therefore minimising repetitive value-checking code. I've reworked mine to suit your variable names:
function createRadioOption($name, $value, $onClickMethodName, $labelText) {
$checked = '';
if ((isset($_POST[$name]) && $_POST[$name] == $value)) {
$checked = ' checked="checked"';
}
echo('<input onClick="'. $onClickMethodName .'();" type="radio" name="'. $name .'" value="'. $value .'"'. $checked .' /><label>'. $labelText .'</label>');
}
<div id="button_set1">
<?php createRadioOption('button', 'Yes', 'show_seq_lunid', 'question1'); ?>
<?php createRadioOption('button', 'No', 'show_list_lunid', 'question1'); ?>
</div>
<div id="button_set2">
<?php createRadioOption('button1', 'Yes', 'os_hpux', 'question2'); ?>
<?php createRadioOption('button1', 'No', 'os_others', 'question2'); ?>
</div>