- If you use a lot of logic in your code or you have a lot of evolution in your code, don't event think of php. Use java or another typed language or you will loose a lot of time debugging "compilation level" code.
As of php5, there is support in php for types and interfaces. Thanks for just blindly trolling.

"- What make PHP popular, is that mistakes you make in you code are "erased" after each call - so even a entry-level developer can develop something without breaking the system. But if you need performance, it means you need good cache management, and php in not very good at this level. A java server run call as an application - so can share information, a php server run call as a single process."

What makes php popular is that it is user friendly. Instead of explicitly having to go through countless mundane type declarations, variables are simplified so that an educated programmer knows exactly what type his or her variable is, and the language is still usable by novices because it follows a natural behavior. As for this "cache management," there are several different implementations for loading scripts into opcodes and maintaing of a cache which are packaged separately from php. Zend Platform includes one implementation, and there are 2 other than can be installed simply with pear. Once installed, the behavior of php is akin to a j2ee environment which incurs a performance hit when JSP is compiled, and then loaded into jvm from that bytecode. The only difference is that the php "vm" translates from source and java from bytecode. Of course both both languages offer a way to load these two into the "vm" upon deployment. You can manage "application level" persistantance through this cache as well. Although, most programmers worth their weight realize that data belongs in a database.

You see, there's a difference in philosophies with php and Java. Instead of forcing a rigid framework that forces you to abstract HTTP with cute caffeinated terminology to the infinite levels of obscurity, php offers a simple programming model that acknowledges http and can be advanced when it needs to be. It's not alone in this as other apache mod_ languages do this as well, but I've found that php keeps the more close to the KISS principal than others. I'd like to draw attention to some notable
non-enterprise grade' applications out there such as, digg and flickr, that are running php, and youtube is running off of python. Java biggotry seems to be extremely pointed because they get a fair amount of abuse from the C community who treats them like leapers.