How to get radiobutton variable into php ?

How to get radiobutton variable into php ?


    <div id="radioset">
        <input type="radio" id="radio1" name="radio"><label for="radio1">Choice 1</label>
        <input type="radio" id="radio2" name="radio" checked="checked"><label for="radio2">Choice 2</label>
        <input type="radio" id="radio3" name="radio"><label for="radio3">Choice 3</label>
    </div>

<?php
//     if (radio == Choice 1){
//     include ("file1.php");
//     }
//     elseif (radio == Choice 2){
//     include ("file2.php");
//     }
//     else {
//     include ("file3.php");
//     }
?>

How can I make this process ?