I have a PHP script I wrote for my research that takes stupidly long time to run. Why? I don't know. So on an off chance of finding something useful, I put "PHP profiling" into google.
So it turns out that PHP profiling is a huge topic, there are many websites ready to provide HOWTOs and tutorials for a zillion different techniques. And, like everything in the computer world it seems, the solution is easy and sifting through all useless advice and "type-this-random-thing-into-your-console" is what takes the time.
Here's what gentoo users need to know:
- emerge xdebug
- Edit /etc/php/php-cli/ext/xdebug.ini , set xdebug.enable_profiling="1", and I also had to increase my max_nesting_level to "1000". It took forever to figure this out, ALL the documents say "oh, just put the settings in php.ini.". WRONG. They get ignored in there.
- Install kcachegrind, and use it to load the profile dumps now being written in /tmp/cachegrind*