In a post from Lukas Smith, he gives responses to some of the questions/comments people have to say about PHP, specifically in how it's related to Java.

Whenever someone asks me why PHP is more "agile" than Java, I tell them that in PHP you can break most of the rules your comp sci course told you about and get away with it. Of course this means that you need PHP developers to constantly clean up their code.

He talks about rules for developing in PHP, one being not to change a method so make it incompatible with its parent. He recommends one way to avoid this - the E_STRICT warning to protect against possible conflicts and issues (the same kind of functionality in PHP6 is in E_FATAL though).

Please, lets get the sense back here. Lets not make things that are not fatal an E_FATAL. Lets use E_STRICT for the pedantic, lets add a E_DEPRECATED for all things deprecated. Lets not kill what makes PHP more agile than those other languages that think they know what I should be spending my time on.