Open function reference when pressed F1

When one needs to know what a function does. There are two ways of doing it.
1. With a reference help file (chm), searching for the function there
2. Going to the language reference site (i.e.: php.net) and search there

So the suggestion is to add a setting to set a help file path which sublime will open and search for the function behind the cursor and the when F1 is pressed.
Or if not configured, open a browser and go to the language site and it's function page