PHP
From Joomla! Documentation
Outdated translations are marked like this.
PHP is a computer scripting language designed for creating dynamic web pages. PHP is widely-used for web development and can be embedded into HTML. It generally runs on a web server, taking PHP code as its input and creating web pages as output. Joomla! is primarily written using the PHP language. For more information, see Where can you learn about PHP?
参照: PHPを学ぶには?