Clockwork - php dev tools in your browser - server-side component
Xdebug Profiling Web Frontend in PHP
The Phoronix Test Suite open-source, cross-platform automated testing/benchmarking software.
XHProf is a function-level hierarchical profiler for PHP and has a simple HTML based user interface.
The Developer Tools Panel for WordPress
Database Profiler for Laravel Web and Console Applications.
[NOT MAINTAINED ANYMORE] Lightweight profiler for PHP (based on facebook/xhprof) -- use Blackfire instead