I'm using php, and I am trying to search my subdomains for 2 different inquiries. First I would like what ever check box I choose to enter in it's value into the subdomain field. Also if I check both boxes I would like it to display results into two iframes instead of one. Any idea on how to complete this?

Code:
<html>
<head>
<title>Discussions</title>
</head>
<body>
<form id="search" action="http://<?php $_POST["subdomain"]; ?>.website.com" method="GET" target="contentframe">
			<div>Search</div>
			<input type="hidden" name="areaID" value="220">
			<input type="hidden" name="subAreaID" value="">
			<input id="query" name="query" size="100"><br>
			<select name="catAbb">
				<option value="sss" selected="selected">Electronics
			</select>
			<input id="go" type="submit" value="&gt;"><br>
			<input type="checkbox" name="subdomain" value="PSP" /> PSP<br>
			<input type="checkbox" name="subdomain" value="PS3" /> PS3
		</form>
		
		<iframe height="50%" width="50%" name="contentframe" frameborder="0">
</body>
</html>