BETA 26 Extremely slooooooooow..

[AlexanderT]

That is part of stress testing though.

Stress testing won't tell you what functions or parts of your PHP code perform or underperform.

When a page under performs, you look at the underlying code to find out why. The developers are running constant unit tests and frequently looking at those functions.

Unit testing is done to show that individual parts of your code are running correct. "Looking" at the functions is correct - and I was referring to profiling as a way to _look_ at such statistics as time spent within each function, how much memory has been used for individual parts of the code, etc. This is how you find bottlenecks in your code without just looking blindly at the code and hoping for the best.

Correct, Xdebug's profiler is just one tool (a mighty one, though). Other more commonly known ones include DBG (as used in PhpEd) and the one in Zend Studio.

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xdebug is used too, some improvements were made based on this tool.

I don't have vB 5, but I can imagine a profiler's statistics output gives a good picture of the existing bottlenecks.