I sometimes use microtime() to see how fast parts of my script are running. It is usually something along the lines of this:

PHP Code:

$start = microtime(true);

// code block

$time = microtime(true) - $start;
echo '<p>',round($time, 4),' seconds.</p>'; 


The weird thing is that sometimes when I view the page I will get negative times, like -0.1373, and other times I get positive times, like 0.095. This occurs just from simple browsing and refreshing, and without changing the code. Does anyone have any clues as to why this might be happening?

If the script executes too quickly, then you run into issues of accuracy. For instance, a computer doesn't do so hot storing 10^(-100000000000000000) and will cause you to get a negative where you ought to get a positive (for the mathematically challenged, that number IS positive -- it's the exponent which is negative). So, if you're trying to measure a script's speed which executes faster than .001 seconds, you'll have such weird issues.

Heh. I think the problem was that I was using PHP 5 locally, and I forgot that I still had PHP 4 on the host which I was working on. I don't think there was a bool parameter in PHP 4.

[QUOTE]I don't think there was a bool parameter in PHP 4.[QUOTE]
True, it was added in PHP5.

If you want to profile your application, I recomand you Xdebug, if you can install it.
Look at this thread: http://www.webmaster-talk.com/php-fo...tml#post466576