Código PHP:
<?php
if (isset($_POST['campo']))
{
foreach ($_POST['campo'] as $key => $val)
{
echo "ID: $key, VALUE: $val<br />";
}
}
?>
...
<input type="checkbox" name="campo[<?php echo $llave; ?>]" value="<?php echo $valor; ?>"/>
<input type="checkbox" name="campo[<?php echo $llave2; ?>]" value="<?php echo $valor2; ?>"/>
Saludos.