PHP consists of extensions. PHP extension is a self containing module that provides some particular functionality, such as sessions or accessing databases.
Introduction chapter will introduce the categorization of the PHP extensions, where they can be found and how you can install them.
PHP date extension provides functions and classes for working with dates and time.
PHP session extension provides functions and classes for persisting data between requests. Learn more about sessions in PHP and session extension.
Access databases with PHP.
Regular expressions in PHP.
Phar (PHP Archive)