Serving direct static image vs via php

Serving static files is the native behavior of nginx, and when we use
gateway for scripting, it needs more works by nginx. Thus, loading a php
file should take more time than loading an image file.

I compare the speed of loading an image file with serving via php by

header(‘Content-Type: image/jpeg’);

Surprisingly (at least to me), the speed of loading the image via php
was 50 - 70% faster than loading the original image file directly. What
is the reason for this peculiar behavior?

I tested with Pingdom. The difference was in Receive step, which is
associated with downloading the data.

Posted at Nginx Forum:,224228,224228#msg-224228