irontec have just launched an open source project to bring PHP to Android platform. PHP for Android project (PFA) aims to make PHP development in Android not only possible but also feasable providing tools and documentation. The project already have an APK which provides PHP support to Android Scripting Environment (ASE). To get started you can follow the screencast

APK and source code both available at http://phpforandroid.net. Minimum requirement to get PHP for Android running is Android 1.5 phone or emulator. There is even an unofficial ASE build with PHP 5.3 support included.

Source: http://mobile.phpmagazine.net