a.php:

<form action="b.php" ...>
<input type="radio" name="radioname" value="1" />
<input type="radio" name="radioname" value="2" />
<input type="radio" name="radioname" value="3" />
</form>

b.php:

可以用$_GET['radioname']取得radio值，如果表单以POST方式提交，则用$_POST['radioname']获取