Debugger

Hello: I have been browsing the web for a good solution to debug php code, I have found several ones, but none of them meet my requeriments. I create a development tool for PHP (QaDRAM Studio) and I want to be able to debug php code with it, my question here is: Why PHP 4 has no built-in debug features? This will simplify the setup for debugging php code and will allow php development tools provide debug support in a convenient way, instead force the user to change the php.ini file to support debug and to don't be able to debug every time the php version changes. I have examined DBG and it's the one that fits my needs better, but there's not too much information on how to use it and what I have found is not complete. Also requires to load a 'listener' to be able to debug remotely. The Komodo solution looks nicer, but is propietary. Any help or comments? Regards.