<?php
if(!$_POST){
echo '
<form method="post" name="radio">
Избор1 <input type="radio" name="radio1" value="Избор1"><br />
Избор2 <input type="radio" name="radio1" value="Избор2"><br />
<input type="submit" value="Избор?">';
}
else{
$radio = $_POST['radio1'];
echo "$radio";
}
?>