The Platform.sh blog has a post showing you how to create flamegraphs with XHProf for your application's execution and overall performance. A "flamegraph" is just a different sort of graph stacking up the execution times for the methods and functions in your application so they look more like a "flame" than just numbers.

One of the most frequent needs a web application has is a way to diagnose and evaluate performance problems. Because Platform.sh already generates a matching new environment for each Git branch, diagnosing performance problems for new and existing code has become easier than ever to do without impacting the behavior of a production site. This post will demonstrate how to use a Platform.sh environment along with the XHProf PHP extension to do performance profiling of a Drupal application and create flamegraph images that allow for easy evaluation of performance hotspots.

While they show it at work on a Platform.sh instance, the method can be altered slightly to work with your own application with the right software installed. Their example uses the brendangregg/FlameGraph library to do the majority of the graphing work. He shows how to have the code switch on XHProf during the execution and where to put the file for later evaluation. They include the resulting directories and files created from the execution and how to view the resulting (SVG-based) graphs directly in a browser.