Hi, I am an old PHP4 programmer; at the moment I don't see the point to switch to PHP5 since it would require some learning curve, but what are the real differences between the two versions? Is there a real improvement? As far as I know the only difference is for the implementation of an object oriented programming structure, but I don't know of further innovations. Any help is greatly appreciated!
Have a read here: http://www.webmaster-talk.com/php-forum/78717-differences-between-php4-and-php5.html
You really should check it out. There are quite a few differences. I myself was a 4 guy, but I starting looking ahead and getting into 5. There is alot of good shortcuts that 4 doesn't have and alot more magic methods. The learning curve really didn't even seem to exist to me, it was just really easy to pick up on and use. No more than a few days reading over and learning 5 and I use it regularly and efficiently.
PHP 4 is dead. The support for it ended officially this year. And as xxKillswitch said, there are a lot of new and very useful functions which you should not miss. (SimpleXML being my favorite example.) Update... it isn't much effort, and most scripts written for PHP 4 will still work with PHP 5, so you have nothing to lose.