How do I verify if radio button is checked/ unchecked with PHP?

I have two text boxes, box1 and box2, and two radio buttons, radio1 and radio2. Well, my intention is, if i check radio1, box2 becomes disabled, and if i check radio2, box1 become disabled. How to do that?

 

This might help: http://www.homeandlearn.co.uk/php/php4p10.html

 

That is clientside behavior you are describing, so you need to use javascript.

Something like:

<input type="radio" id="r1" onclick="enable(1);" /><input type="text" id="t1" /><br />
<input type="radio" id="r2" onclick="enable(2);" /><input type="text" id="t2" /><br />
<script type="text/javascript">
function enable(n){
  for (var i=1;i<=2;i++){
    document.getElementById('t'+i).disabled = (i!=n);
  }
}
</script>

Code (markup):