Use WML to talk to phones
http://www.zend.com/zend/tut/wap.php
but it also depends on the browser type in the phones. New phones can handle XML / CSS. You can use PHP to build a xml page and send it to the user using CSS to format the data one there.
You would have to detect the phone type (as not all phones react the same) to send the appropriate CSS (WAP/WML may be a better option here, XML for PDAs)
hth
