Question

My signup for looks like that:

<input type="radio" value="a">a
<input type="radio" value="b">b


<select name="group">
<?php
for ($i=1; $i<=4; $i++)
{
    echo '<option value="'.$i.'">'.$i.'</option>';
    }
?>
</select>

What I wanna do is, if selected a, “group” select menu options will be, in range [1;4], if selected b then [5;9]. How to change php on the fly? is it possible with js?

Answer 1

First of all the radio buttons should be give a common name so that they will work a radio buttons.

Markup change

<input type="radio" name="selectGroup" value="a">a
<input type="radio" name="selectGroup" value="b">b

JS

$(function(){

   $("input[name=selectGroup]").change(function(){
      var $select = $("select[name=group");
      var start = $("input[name=selectGroup]:checked").val() == "a"?1:4;
      var end = start + 4;
      $select.empty();
      for(;start < end;start++){
        $select.append("<option value='"+start+"'>"+start+"</option");
      }
   });


});