oppure puoi chiamarli così:

<input type="radio" name="params[$id][act]" id="act$id" value="on" checked />
<input type="radio" name="params[$id][act]" id="act$id" value="off" />

<input type="radio" name="params[$id][sh]" id="sh$id" value="on" checked />
<input type="radio" name="params[$id][sh]" id="sh$id" value="off" />

e ti riprendi l'id con foreach($params as $id=>$value)