I have a large web application idea that I would like to work on, which will require secure database interactions, file creation and editing abilities, speed, and output html. It needs to be able to run on a webhost, not a self-run server. What would be the best programming language to use to create it? I am not looking for 'easiest', I am looking for the most useful for the type of web application I wish to develop.
EDIT: It needs to be able to run on linux.