Well, the synatx error would not be the cause of the problem (so to speak). I suspect that you just saw a blank page because of the syntax error. that would be because you have error reporting turned off. (Good for security, bad for troubleshooting/development).
Apache probably is intutive enough to see the INDEX.xxx lacking a formal index.htm (html) page and presents that instead. Not quite sure here though.
What do you mean by a syntax checker? There are several programs that provide you with feedback on your syntax. Typically they use color hightlighting to identify things like functions, variables, constants, constructs, etc… Ultimately, the true syntax checker will be the web. Try it and see.