While the appropriate tools ensure effective and efficient performance optimization, a good PHP profiler monitors your production environment, and helps you find the impact of your optimization efforts on end users.
As an easy-to-use PHP monitoring solution, AppDynamics for PHP is designed for production environments. AppDynamics, helps you detect bottlenecks, effectively monitor your PHP code, and drill down to the class to ascertain root cause.
Care.com uses AppDynamics to keep the site's critical applications responsive.
PHP Performance Crash Course, Part 1: The Basics
"We all know performance is important, but performance tuning is too often an afterthought. As a result, taking on a performance tuning project for a slow application can be pretty intimidating – where do you even begin? In this series I’ll tell you about the strategies and technologies that (in my experience) have been the most successful in improving PHP performance. To start off, however, we’ll talk about some of the easy wins in PHP performance tuning. These are the things you can do that’ll get you the most performance bang for your buck, and you should be sure you’ve checked off all of them before you take on any of the more complex stuff...."
Top 5 PHP APM Tips & Tricks
"This article series has covered a lot of ground: it presented an overview of application performance management (APM), it identified the challenges in implementing an APM strategy, it proposed a top-5 list of important metrics to measure to assess the health of an enterprise PHP application, and it presented AppDynamics’ approach to building an APM solution. In this final installment this article provides some tips-and-tricks to help you implement an optimal APM strategy. Specifically, this article addresses the following topics...."