Y por que pones <table method="post"...> ? Deberias poner form.
Código PHP:
<?php
echo "
<form method='post' action='radio.php'>
<table>
<tr>
<td>Valor 1:</td>
<td><input type='radio' name='Item1' value='1.1'>1.1</td>
<td><input type='radio' name='Item1' value='1.2'>1.2</td>
</tr>
<tr>
<td>Valor 2:</td>
<td><input type='radio' name='Item2' value='2.1'>2.1</td>
<td><input type='radio' name='Item2' value='2.2'>2.2</td>
</tr>
<input type='submit' value='enviar'>
</table>
</form>
";
?>
Saludos.