Magento undefined constant-Collection of common programming errors

hi have a problems with magento as it shows me this error when i click sunglasses menu:

Notice: Use of undefined constant id - assumed 'id'  in /var/www/app/design/frontend/glassesonline/default/template/mana/filters/items/list.phtml on line 159

This is code at line 159

Originally posted 2013-11-10 00:16:42.