Ian Bickings’s “What PHP Deployment gets right”
This is a wonderfully written article on how PHP works, and the funny thing is that Ian seems to be more of a Python guy than anything. Needless to say, I learned a few things from reading this …
What people don’t realize is that PHP is effectively a CGI model of execution. People don’t appreciate this because PHP is implemented with mod_php, an Apache module. There are many other modules like mod_perl (the first of these mod_language modules), mod_python, mod_ruby, etc. None of these other modules are like mod_php. This has led many a commentator astray because they don’t get this. This is because the PHP language was written for mod_php. Perl, Python, Ruby — none of them were written to be used as an Apache module. You can’t take one of these existing languages and just retrofit it to be like PHP or like mod_php.
PHP processes can leak memory like crazy. It doesn’t matter because they only leak memory for one request.
- This one helped me understand why Ruby On Rails and its fast-cgi implementation is so slow —->.
Most of the language (PHP) is implemented in C, in a shared library. In comparison Python has “batteries included”, but those batteries are largely written in Python. Python code is not shareable, and can take time to load up. So while a single Python CGI script might be small, it probably imports lots of code which would have to be loaded each request. PHP scripts actually are small. (Stuff like PEAR changes this by adding substantial libraries written in PHP, but also seriously effects PHP performance.)