Measurement serial to RasPi / live data with PHP ?


I want to measure 4 voltages with my Mega which works allready fine.
But now I want that the measurement results are transferd serial to RasPi.
On the RasPi is a Apache Server running and I want to have a PHP for
showing the measurement results on a webpage live.
Only the results should shown live, a complete page refresh I don`t want.

This is of course only a local solution!

I didnt found something like streaming data etc.
An easy example would be very nice!