GET UNTICKED CHECKBOXES

<?php
#test.php
 
if ($_SERVER['REQUEST_METHOD'] == 'POST' && $_POST['mailinglist']){
 
	foreach($_POST['mailinglistPre'] as $mailinglistPre) {
		$key = in_array($mailinglistPre, $_POST['mailinglist']); 
		$key = ($key) ? '1' : '0';
		echo $key;
 
 
	}
 
}
?>
 
<form id="form-body" action="test.php" method="POST">
	3<input type='checkbox' name='mailinglist[]' value='mailinglists/3.obj' /><br/>
	 <input type='hidden' name='mailinglistPre[]' value='mailinglists/3.obj' />	
	4<input type='checkbox' name='mailinglist[]' value='mailinglists/4.obj' /><br/>
         <input type='hidden' name='mailinglistPre[]' value='mailinglists/4.obj' />
	5<input type='checkbox' name='mailinglist[]' value='mailinglists/5.obj' /><br/>
         <input type='hidden' name='mailinglistPre[]' value='mailinglists/5.obj' />
	<div class="form-surround-notext">
	    <div><input type="submit" value="Unsubscribe" id="submit" /></div>
	</div>
</form>