I have tried few and they only highlight HTML/Javascript even though they offer shortcuts for php tags they dont have PHP highlighting. someone knows of one that highlights php?
P.S. dont get me wrong i am not going to program on phone, just in case i need to fix error or two on the go...
Maybe you can try Eclipse. Here's a link for the php version of Eclipse:
http://www.eclipse.org/downloads/packages/eclipse-php-developers/heliosr
Notepad++ - supports most languages
You can use DroidEdit (disclaimer: I'm the developer): https://play.google.com/store/apps/details?id=com.aor.droidedit
Another alternative is Jota: https://play.google.com/store/apps/details?id=jp.sblo.pandora.jota
For Java, Aide is a great editor that even allows to build your own apk: https://play.google.com/store/apps/details?id=com.aide.ui
All of them work great in your phone but work better if you have an external keyboard or a Transformer Prime.
You can check out my app - Android Web Developer. It contains a lot features, e.g.:
I hope it will be useful for you