Hi thanks a lot for your response @israel.cefrin.
I would like to know how send the messages from a Class PHP code. I have seen that some parts of the OJS code have the print_r and var_dump as means for debugging purposes. But I dont know where to see that messages? I have configured my php.ini file to set the path to a log file, then I execute OJS from browser but I dont find anything about the debug messages.