validation, radio button, and loops?

[eluser]alanphil[/eluser]
In my view I'm creating a list of concerts, like this:

Code:

<?php foreach ($concerts as $row): ?>

&lt;input type="radio" name="concert_selection" value="&lt;?=$row-&gt;id?&gt;">&nbsp;&lt;?=$row->concert_name?&gt;, &lt;?=$row->concert_date?&gt;, &lt;?=$row->count?&gt; pair(s) of tickets available<br />

&lt;?php endforeach; ?&gt;

I'm trying to add validation to keep the selected radio button selected, if some other field fails validation. I've tried many variations of the following from the user guide:

Code:

<input type="radio" name="myradio" value="1" <?php echo $this->validation->set_radio('myradio', '1'); ?> />

When I try the following, the radio button isn't set after validation:

Code:

<?php echo $this->validation->set_radio('concert_selection', "<?=$row->id?>"); ?>

I've tried many variations of the above. What am I missing?

Alan