Thanks for the response so far...
... if the difference is negligible for little code snippets on a web site, but PHP5 is properly object-oriented, then I guess it makes more sense to learn PHP5. I suspect that by the time I learn enough to do anything useful that is unique to PHP5, it will be used more often.
"We are all born originals -- why is it so many of us die copies?"
- Edward Young
Stay simple until you need it
I hadn't seen that migration page Jay linked. The differences are even smaller than I thought.
My recommendation is learn the syntax, learn the functions, but only what you need to maintain your site. By the time you know enough to start getting all "enterprisey" you'll want to throw out your early efforts anyway.
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