Not having a long history of PHP and MySQL programming, I find it rather difficult to work with updating old code (e.g. old modules) to be compatible with the latest versions of PHP and MySQL, since I don't know which functions etc are not supported in different versions (yes, I can look at the error log in XOOPS, but that may just show the symptom and not the root cause of a problem, if you know what I mean).

It seems to me that this shouldn't be an uncommon situation, so my question is, are there any tools/environments which let's you check your code to identify syntax errors, calls to deprecated functions etc?

I have been looking all over, but haven't really found any. Can it really be so, or am I just looking in the wrong places?