I couldn't disagree more. First of all, you cannot really compare Ruby on Rails, and application framework, with PHP, a server-side scripting language. That would be a bit like comparing C++ with Movable Type.
Secondly, Ruby on Rails is slow, partly because it relies on lots of other technologies to work. For example, it has to access database tables in order to generate classes at runtime - very weird.
Finally, PHP is getting better and better. The object support and features introduced with PHP5 have enabled it to compete with Java Server Pages in the enterprise-level world. It doesn't rely on other technologies to do things, but it can also work with just about anything.
A word about backward compatibility - certain things left over from PHP3 were improved upon in PHP4. Some things left over from PHP4 were deprecated in PHP5. In PHP6, most of the deprecated things will be removed. What is wrong with that? That seems to me to be a sensible upgrade path if you ask me.
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