Somehow PHP won't create the "logs" folder by itself... and that's what we need to do:

1. Created the "logs" folder in the correct location (for instance, C:\xampp\php\logs).

2. Restart Apache using XAMPP control panel (stop and start).

Then when an error occurs the file will be generated fine and you'll be again able to open the PHP logs from XAMPP console

To test that it's working you can create a fatal error by using

trigger_error("Some info",E_USER_ERROR);

In my case I solved this problem by making the main settings made in the question, with only two changes:

track_errors=On
error_reporting=E_ALL & ~E_DEPRECATED & ~E_STRICT
log_errors=On

change 1:

error_log="C:\xampp\php\logs\php_errors.log"

in the documentation it says that these methods are deprecated, so it is disabled by default and with the wrong directory.

change 2:

Create the folder 'logs' in: C:\xampp\php

This worked for me, I hope it will be useful.

If you are sure that you are using the right config option to set the log path, it might be that PHP is not writing to the error log because of a certain type of syntax error. Put your code through a syntax checker like http://phpcodechecker.com/