Coding productivity benchmarks?

I've been searching around for productivity benchmarks for PHP programming. The only references I can find for it are in for-pay publications. I've ended up becoming a PHP developer more out of happenstance than anything. I've been doing it for a couple of years now, but... I don't really know how 'good' I am at it. The place I work has always had extremely unreasonable expectations for worker productivity, and I'm trying to fight that. I've recently been called into another job interview, and part of the interview is a coding assignment. Some of the documentation suggests that this assignment should take about 40 minutes. A rough overview of the 'assignment' - a simple Document Management System - is: * new user registration and existing user login * admin-level user management * document upload and download * review and suggestion * a conditional matrix of 5 document conditions vs 3 user levels * 6 input forms * 2 listing layouts with fix sorting * conditional access to changing document conditions based on user levels It took me about 4 hours to completely satisfy and debug the assignment specs with an OK interface. This was with plenty of code copy/modification from other web apps I've done before, or other online resources. I ended up spending nearly 4 more hours futzing around with the interface to get something really nice. So, am I just a pretender? Are there people out there that can really bust out a basic DMS in 40 minutes? If anyone does have some basic PHP programmer productivity benchmarks, or knows where I can get ahold of them, I'd sure appreciate it. This issue of productivity expectations has really gotten under my skin, and I need to know whether or not I should be doing this for a living. Thanks, -Derrick