I would like to crate a web-solution for price matching, a solution similar to Pricerunner.
My question is what tool would be best to use? I would prefer Flex or Flash Builder with java back-end but is it the best?
It depends on your suite of developers and money available. There is no “best”, there are simply solutions that are easier to implement depending on what your develoeprs skills are. If you have developers that are good at Java but don’t know PHP…don’t use PHP. If your developers are good at PHP and don’t know Java…don’t use Java.
As for the site, I took a look at the Pricerunner site and it isn’t a Flex or Flash based site, it’s just a normal script based site, probably PHP (and poorly done on the backend, that source code is hideous). You should probably hire a regular web developer to make the site and add Flash where it will improve the site’s capabilities, not develop the entire site in it (unless that’s all your developers know).