What are some good PHP profilers that can be used?

Low level profilers - These are modules which are loaded into the php executable, and therefore are a bit harder to setup, but they provide solid results.

• http://pecl.php.net/package/xhprof
• http://xdebug.org/

PQP is a code-based profiler. While probably not as accurate as the low-level profilers mentioned above, it may be all you need if you are looking for some simple metrics.

• http://particletree.com/features/php-quick-profiler/

I use XDebug and WinCacheGrind to profile php.