I had to take one of these proveit.com test today for PHP5. I cheated, just so you know. I mean, do you know by heart all the array functions and what they do, and all their quirks? What about all the quirks of the "final" keyword? How about doing bitwise math or scientific notation in your brain?
Didn't think so.
They use a Java applet, and I think a Java applet can detect everything on your screen that you're doing? I'm not 100% certain, but I thought that was possible? So, I contained the test in a VM while I did my lookups and tests in another window. And I moved as fast as humanly possible, typing keys just as fast as I could in case the thing was timed. In most cases I would either lookup the answer in the php.net site or run a test with the code they provide.
So, anyway, I got a "C" grade even with cheating by finding answers on the php.net site and running the actual code samples. This tells me either one of two things. A) the exam has a time-limit per question, B) the exam answers are not correct. Trust me -- I've worked with several groups studying for various Sylvan Prometric exams and more than once through process of elimination we determined that several of their exams had incorrect answers -- at least two on each exam.
Therefore, the only way to really get through this exam with a B or higher, I'd guess, is if you answered questions by guessing, but did smart guessing by process of elimination on what the answers would NOT be. That way, if their answers are wrong, you might luck out and hit their wrong answer. And of course I recommend moving through this exam fairly rapidly -- I spent one hour and I recommend you try and do it faster.
And I wouldn't doubt that all these online exams throw in like 4 bogus answers just to see if anyone gets 100% on their exams. If you did get 100%, then you might be cheating, you see. So I wouldn't doubt that one bit.