I dont use it. I already had eclipse/php and WAMP when I bought Flex
does Flex/PHP install a local server for you or do you have to install WAMP (or MAMP or LAMP)?
this might help
I do not have a 'concise' answer for you - in fact I am not using FB 4.5 for PHP. I started using FB 4 around 8 months ago. I installed a 'WAMP' thing, called 'EasyPHP'. That actually went pretty smoothly. I did the whole thing on my personal laptop running Windows 7. I 'hooked up' FB to the PHP side using the built in data services wizards and such, as I imagine you are trying to do. I too had to 'fight' a bit, but found most of the answers scattered around the Internet. Had to tweak a few settings here and there in various files, and viola, it worked.
I have resisted upgrading to 4.5, and especially the 4.5 "for" PHP, only becuase of the great expense. It seems like a lot of money to pay for 'integrated, round-trip debugging'. I already can debug the PHP side 'independently' of the FB side (from inside the Eclipse+PHP plugin free toolset), which, for most SQL situations is good enough. I simply set up a 'test page' in PHP and use that to 'call' the various functions I write.
On the FB side, I gave up on using the 'built in data services wizard thingies' because they simply could not get the data-type mappings correct between the two sides. Also, the "value objects" things (really just a fancy data-object class definition) seeme overly complex and inflexible, i.e., they would re-code themselves after every change I made to the PHP side. I prefer a more 'lean' approach, and one that I control 100%. So far I am able to do everything I need using my own 'value objects' (simple classes).
So...as you can see, I may not be able to help much, but, if you can explain some of the details of what is failing, maybe I can provide a bit of assistance. From what I understand, the big difference between 4.5 and 4.0, at least on the PHP side, is that the 'introspector' is a bit more accurate now and of couse there is the 'round-trip' debugging and 'awareness of each other's objects/definitions' while in PHP or FB.
Finally, as best I can tell, after 8 months of 'experimenting' with Flex and PHP, there are simply not many people doing it, or, at least not that many doing it that participate on this forum and who have practical experience, especially with the more 'recent' releases, i.e., 4.0, 4.5. I would encourage you to scan the rest of the Internet...there *is* knowledge out there...but it can difficult and slow to get.