Programming PHP

changes you make to your code as you attempt to improve its speed—we show you
how to time individual portions of a page in the next section, but ultimately these
microbenchmarks don’t matter if the overall page is still slow to load and run. The
ultimate proof that your performance optimizations have been successful comes
from the numbers that ab reports.
Profiling
PHP does not have a built-in profiler, but there are some techniques you can use to
investigate code that you think has performance issues. One technique is to call the
microtime( ) function to get an accurate representation of the amount of time that
elapses. You can surround the code you’re profiling with calls to microtime( ) and
use the values returned by microtime( ) to calculate how long the code took.
For instance, here’s some code you can use to find out just how long it takes to produce
the phpinfo( ) output:
Reload this page several times, and you’ll see the number fluctuate slightly. Reload it
often enough, and you’ll see it fluctuate quite a lot. The danger of timing a single run
of a piece of code is that you may not get a representative machine load—the server
might be paging as a user starts emacs, or it may have removed the source file from
its cache. The best way to get an accurate representation of the time it takes to do
something is to time repeated runs and look at the average of those times.
The Benchmark class available in PEAR makes it easy to repeatedly time sections of
your script. Here is a simple example that shows how you can use it: