Debug Bar Extension for the Timber Library
Easy debug for your JSON API.
The Debug component provides tools to ease debugging PHP code.
The VarDumper component provides mechanisms for walking through any arbitrary PHP variable. It provides a better dump() function that you can use instead of var_dump().
Xdebug — Step Debugger and Debugging Aid for PHP
Debugging suite for Magento
Laravel Debugbar (Integrates PHP Debug Bar)
A Guzzle middleware that lets you log HTTP requests in the PHP debugbar timeline.
Php Debugger to run in terminal to debug your code easily.