Textastic 6 is a new universal app that works on both iPad and iPhone: https://geo.itunes.apple.com/us/app/id1049254261?ct=feedback&at=11lNQP&pt=15967&mt=8
I submitted the iPhone version to Apple 10 days ago. I hope Apple approves it this week.
You can find the website with screenshots of the iPhone version of Textastic at http://www.textasticapp.com/iphone.html
There is also an updated manual available at http://www.textasticapp.com/iphone/manual/
The iPhone version of Textastic is available on the App Store: https://itunes.apple.com/us/app/textastic-code-editor-for-iphone/id550156166?mt=8
Customer support service by UserEcho