What is PHP?
PHP is a widely-used general-purpose scripting language that is especially suited for Web development and can be embedded into HTML.
Where can I find more information?
Official Site http://www.php.net
So what's the connection between PHP and cocoon?
See: PHPGenerator
The PHPGenerator has been deprecated however, since it didn't work properly, nobody was able to support it, and hardly anybody used it.
What may the future hold for PHP <--> Java interaction ?
JSR223 Scripting Pages in Java Web Applications