Thanks SABmore. I have looked at CodeIgniter before, but my web application is very simple (in terms of the code I am deploying). I'm a bit reluctant to choose a framework just for a log-in script but will look at Ion Auth.
Am I right in thinking that (a) there is no good, working, error-free way script/method of doing user management or (b) a tutorial or guide that explains building something fully fledged - with things like proper security and validation, etc.
There are many tutorials out there, but reading nearly every guide's comments reveals bugs, or things left out.