Have you at all been paying attention? PHP 5.6 has namespaces, closures, lambdas, generators, autoloaders, traits, function argument splats, sane array literals - basically everything the authors ever saw in good use, anywhere.

There is hardly any difference between PHP 4 and 5, except internals. The only real big difference between PHP 3 and PHP 4 is a different class syntax.

Well, I switched from PHP to JavaScript, so, no lol.

I thought the class system was improved with 5 and was unusable with 4. At least that was what I read. I started with ... PHP 5.2

PHP 5.6 and what Facebook are doing with HHVM/Hack are (in the latter case, literally) entirely new languages than PHP4 or even pre-5.3, and with the PSR community standards body, Composer/Packagist and the massive amounts of interoperation between libraries nowadays, it's actually enjoyable to code in again :)

5.3 is basically a whole new language. Development is pretty quick and regular ever since 5.4 and the new RFC process.