Commercial debugger?

Hi, Does anyone have the url for a (the only?) commercial php debugger? I visited the website before but have since lost the info and it's not turning up in searches. Also, if anyone has actually used it, I'd appreciate hearing comments and evalutaion. The website gave very little info - other than how to buy it online, so I'm wondering if it would be helpful at least as a learning tool, if not as a serious tool for experienced programmers. Thanks in advance, Brian