Get Id of Items

My customized content types need a link passing its ID to another PHP script. This PHP script looks into database and performs based on the ID. Here is the sample page template:

<div tal:define="itemId context/getId;
                 itemIdUpper python: itemId.upper()">
<a href=""
 tal:attributes="href python: 'http://another.site.com/some.php?k='+itemIdUpper;
                 title itemIdUpper;">Show in Another App</a>
</div>