Running background task from a web server on linux

I have a completely new web project and I'm free to use what language I want as long as it works well on Linux. My background is strong in PHP but I do have experience with Java, C# and a little Python.

I have no problem developing the back-end part of the website in PHP using a framework such as Laravel or Zend. However, there are going to be a lot of background tasks or at least long running background tasks (an hour possibly). I know there are PHP commands I could use to execute PHP scripts in the background when I receive a web request but that just doesn't feel like good design. I'm not adverse to learning a new language either, as long as the learning curve is not too steep. I did consider learning to use Java EE for this but I'm not sure that is necessarily the correct way.

Additionally, some of the guys responsible for data have been considering various solutions, including the use of Cassandra, MongoDB and Hadoop so whatever language I choose would potentially have to have interface into those products as well.

I'm sorry if this might be an open ended question but could someone give me some pointers please? I have been researching on the net for the past 5 hours and seem to be going in circles a little. The background processing will be crunching CSV files, inserting into databases, analyzing data sets etc.