XHProf is a hierarchical profiler for PHP. It reports function-level call counts and inclusive and exclusive metrics such as wall (elapsed) time, CPU time and memory usage. A function's profile can be broken down by callers or callees. The raw data collection component is implemented in C as a PHP Zend extension called xhprof. XHProf has a simple HTML based user interface (written in PHP). The browser based UI for viewing profiler results makes it easy to view results or to share results with peers. A callgraph image view is also supported.
If you are reading this blog post you must be striving to improve the performance of your site. When we speak about performance two things should be taken into account essentially.
I guess it is not much needed to stress as how essential the response time plays in deciding the success of a website. Apache the prominent Web server plays a key role in this connection.
One of the interesting assignments I took recently is troubleshooting a slow Drupal 7 site. The site was hosted on our AWS micro instance. I'm sure the problem was not to do with server load as the other sites hosted on the same server were doing great for both authenticated and anonymous users.