Programming PHP

Before you begin optimization, ask yourself whether you need to optimize at all. Too
many programmers have wasted hours wondering whether a complex series of string
function calls are faster or slower than a single Perl regular expression, when the
page that this code is in is viewed once every five minutes. Optimization is necessary
only when a page takes so long to load that the user perceives it as slow. Often this is
a symptom of a very popular site—if requests for a page come in fast enough, the
time it takes to generate that page can mean the difference between prompt delivery
and server overload.
Once you’ve decided that your page needs optimization, you can move on to working
out exactly what is slow. You can use the techniques in the upcoming “Profiling”
section to time the various subroutines or logical units of your page. This will give
you an idea of which parts of your page are taking the longest time to produce—
these parts are where you should focus your optimization efforts. If a page is taking 5
seconds to produce, you’ll never get it down to 2 seconds by optimizing a function
that accounts for only 0.25 seconds of the total time. Identify the biggest time-wasting
blocks of code and focus on them. Time the page and the pieces you’re optimizing,
to make sure your changes are having a positive and not negative effect.
Finally, know when to quit. Sometimes there is an absolute limit for the speed at
which you can get something to run. In these circumstances, the only way to get better
performance is to throw new hardware at the problem. The solution might turn out
to be faster machines, or more web servers with a reverse-proxy cache in front of them.
Benchmarking
If you’re using Apache, you can use the Apache benchmarking utility, ab, to do highlevel
performance testing. To use it, run:
$ /usr/local/apache/bin/ab -c 10 -n 1000 http://localhost/info.php
This command tests the speed of the PHP script info.php 1,000 times, with 10 concurrent
requests running at any given time. The benchmarking tool returns various
information about the test, including the slowest, fastest, and average load times.
You can compare those values to a static HTML page to see how quickly your script
performs.
For example, here’s the output from 1,000 fetches of a page that simply calls
phpinfo( ):
This is ApacheBench, Version 1.3d apache-1.3
Copyright (c) 1996 Adam Twiss, Zeus Technology Ltd,
http://www.zeustech.net/
Copyright (c) 1998-2001 The Apache Group, http://www.apache.org/
Benchmarking localhost (be patient)
Completed 100 requests
Completed 200 requests
This is the Title of the Book, eMatter Edition
Copyright © 2002 O’Reilly & Associates, Inc. All rights reserved.
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