JQuery Mobile with (Tera)WURFL

http://www.google.co.in/search?q=developing+mobile+interface+with+php&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=ffl

http://dbapi.scientiamobile.com/wiki/index.php/Main_Page
device detection: http://wurfl.sourceforge.net/  simple class: http://code.google.com/p/php-mobile-detect/
Mobile Interface creation:
  http://jquerymobile.com/
Tera-WURFL from http://stackoverflow.com/questions/2502790/developing-mobile-app-iphone-blackberry-android-for-an-existing-website

http://stackoverflow.com/questions/1848885/where-to-begin-with-smartphone-web-development/1938164#1938164

Fire fox User Agent Plugin

http://techie-buzz.com/tips-and-tricks/emulate-mobile-browser-in-firefox.html

Other tools
http://sixrevisions.com/tools/10-excellent-tools-for-testing-your-site-on-mobile-devices/

mobile phone W3 validator

http://validator.w3.org/mobile/