DBG Debugger: http://dd.cron.ru/dbg
A PHP extension that provides debug and profile facilities, released in two forms: free and commercia. The commercial is shipped with Nusphere PhpED. Protoeditor uses the free version of it.
From Quanta+ about: "Our goal is to be nothing less than the best possible tool for working with tagging and scripting languages."
"The future home of the kdewebdev module application pages"
"PHPEclipse is a set of plugins for the Eclipse Framework which provide and integrated IDE for PHP developers."
"Gubed is a cross platform program to debug PHP scripts"
"The Xdebug extension helps you debugging your script by providing a lot of valuable debug information."