radio button value

If an html page contains several radio buttons with the same name (but different values) and NONE is selected (checked), is the value of the radio button element null?

For example, in a form named "st", radio button name "pid", does document.st.pid.value == ""?
Richard KortsAsked:
Who is Participating?

Improve company productivity with a Business Account.Sign Up

x
 
RobConnect With a Mentor Owner (Aidellio)Commented:
if none are selected then yes it's null (not empty string)

What happens for you when you try it?
0
 
Julian HansenCommented:
It's more than null it is not defined.

Consider this code
<form action="reflect.php" method="post">
   <input type="radio" name="testradio" value="1" />
   <input type="radio" name="testradio" value="2" />
   <input type="radio" name="testradio" value="3" />
   <input type="submit">Submit</input>
</form>

Open in new window

reflect.php
<?php
echo "<pre>" . print_r($_POST, true) . "</pre>";

Open in new window


If you don't click any radios you get an empty $_POST array.

There is a trick you can do to get around this

<form action="reflect.php" method="post">
   <input type="radio" name="testradio" value="0" checked />
   <input type="radio" name="testradio" value="1" />
   <input type="radio" name="testradio" value="2" />
   <input type="radio" name="testradio" value="3" />
   <input type="submit">Submit</input>
</form>

Open in new window


In the above we add a 4th input that acts as a default. This is checked by default and if no other buttons are selected then you get a value of 0 coming through.

You can optionally hide this additional radio with styling so it is not visible. It can be useful though if you want the option to de-select a radio - i.e. being able to "change your mind" after clicking a radio to effectively be "none of the above" = which is not practically possible with a standard bank of radio buttons showing only available answers where "changed my mind" would require being able to click "off" a selected radio the way you would a checkbox.
0
 
RobOwner (Aidellio)Commented:
yes on the server side it will not come through (checkboxes) are the same.

Another trick is to include a hidden element with the default value:

<form action="reflect.php" method="post">
   <input type="hidden" name="testradio" value="0"  />
   <input type="radio" name="testradio" value="1" />
   <input type="radio" name="testradio" value="2" />
   <input type="radio" name="testradio" value="3" />
   <input type="submit">Submit</input>
</form>

Open in new window


However, you are correct that on the client side it will be returned as the empty string "", not null
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

All Courses

From novice to tech pro — start learning today.