Kint Debugger makes debugging and dumping variables a more pleasant experience. Kint Debugger integrates seamlessly with the Debug Bar plugin.
Kint is a modern and powerful PHP debugging helper, which requires zero-setup and replaces var_dump(), print_r() and debug_backtrace().
A Debug Bar plugin that lets you trace what plugins are causing database queries.
Krumo is a debug tool able of collapsing array and object values so that it takes less space and let us see only what we really need from complex data
Debug trace for WordPress, including action and filter tracing
Display debug backtraces for every error generated by PHP.