How to check dynamically with radio box is selected in the div - php

Question

I need a dynamic function for checking whether a radio box is selected in the div or not.
Actually I want to show an error message every time an user, without selecting the radio button, presses the next button.
I am working on this page. The ILERI means NEXT.
These are the divs. There are 9 div on the page cited above.
<div id="div2" class="targetDiv">
<a id="back" class="ileri-geri" target="1" >GERİ</a> <h1>Cep Çesitleri</h1>
<a class="ileri-geri" target="3">İLERİ</a>
<div class="urunler">
<ul class="urun">
<li><img src="imagesBOX/items/cepsayisi/0.jpg"></li>
<li><p>Cepsiz</p><input type="radio" name="cep_cesitleri" value="0" /></li>
<li></li>
</ul>
<ul class="urun">
<li><img src="imagesBOX/items/cepsayisi/1.jpg"></li>
<li><p>Tek Cepli</p><input type="radio" name="cep_cesitleri" value="1" /></li>
<li></li>
</ul>
<ul class="urun">
<li><img src="imagesBOX/items/cepsayisi/2.jpg"></li>
<li><p>Çift Cepli</p><input type="radio" name="cep_cesitleri" value="2" /></li>
<li></li>
</ul>
<h1>Cep Sayisi</h1><br/>
<?php foreach($Secondresult As $jcRow): ?>
<ul class="urun">
<li><img src="imagesBOX/items/cep_cesitleri/<?php echo $jcRow->image ?>" /></li>
<li><p><?php echo $jcRow->title ?></p><input type="radio" name="cep_cesitleri" value="<?php echo $jcRow->id ?>" /></li>
<li></li>
</ul>
<?php endforeach; ?>
</div>
</div>
<!----2nd page--->
this is javascript which hides all the div and show the div only based on target attribute of tag .
<script type="text/javascript">
$(document).ready(function(){
$('.targetDiv').hide();
$('#divfirst').show();
$(".ileri-geri").click(function(event){
$('.targetDiv').hide();
$('#div'+$(this).attr('target')).fadeIn('slow');
//alert("Redirecting you to jQuery.com!");
});
</script>
Now I want that, If user click on ILERI button without selecting the radio option, then the error mesg will appear, but the function should dynamically show that it handles all the 9 div on this page.

Answer 1

You can check if at least one item was checked with this:
$(".urun input:checked").length() > 0

Answer 2

$(".ileri-geri").click(function(event){
//you have to detect the visable .targetDiv first
if($('.targetDiv:visible input:checked').length() > 0) {
$('.targetDiv').hide();
$('#div'+$(this).attr('target')).fadeIn('slow');
}else{
alert("Error");
}
});