Debugger:
Please read : https://www.splitbrain.org/blog/2008-02/21-understanding_php_code_better_with_xdebug
Tracer:
Please read : https://www.splitbrain.org/blog/2016-02/27-visualizing_xdebug_traces
Tracer GUI: https://github.com/splitbrain/xdebug-trace-tree