Spurred on by some previous benchmarks [pdf] from Ilia Alshanetsky, Joakim Nygard decided to run some his own benchmarks on the same sort of functionality.

There are numerous discussions in the blogosphere about whether to use echo versus print, if for() is faster than while(), etc. and though the gains are usually very small, I decided to add my thoughts to the debate. I found an article on optimization through coding habits in Ilia Alshanetsky's zend performance slides.

According to his results:

• Calling require_once() 10000 times in a for() loop with an empty file is 4x faster.
• With a simply autoload requiring a class and 10000 loops of new Foo() versus require_once('foo.php'); new Foo() shows that __autoload() is ~3.7 times faster.
• If a class method can be static, declare it static. Speed improvement is by a factor of 4.
• Avoid function calls within for() loop control blocks
• Always, always quote array keys.
• Get rid of 'harmless' error messages - they take time to generate and output.

I am not out to prove Ilia wrong - he knows PHP better than most - and for all I know, they could have optimized those very functions in PHP 5.2. [...] It would appear that there are improvements, albeit small, to achieve from minimal effort. Plus I was surprised by the discrepancies I found compared to Ilia's recommendations.