Method call overhead

Hi! I've measured the overhead for method calls in a variety of environments (Amazon, Travis, and 3v4l). The results are reliable and here's 3v4l <http://3v4l.org/NsjJR>. Some observations. First, as expected, direct calls are faster than static object calls, which are faster than object calls. Second, in absolute times PHP7 outperforms HHVM3 substantially. Kudos, really impressive. My question though is on relative times. Method call overhead is consistently 50% to 150% over a direct call. Is my experiment invalid, or is this overhead expected? Is the overhead in the allocation, deallocation, GC? Cheers, bishop