The PHP Function Extension_Loaded()

If you have written a PHP extension and want it to be loaded into your copy of php, you need to use a function called extension_loaded(). This function takes an extension name as the only argument and returns whether or not it has been loaded. There are a couple of caveats: first, it is not the same as get_loaded_extensions(). The second is that the return value of extension_loaded() can be slow because it has to parse the complex and unstructured header files of the Zend engine. This is not a big deal, but it is something to bear in mind.

Aside from this, the functions in extension_loaded() are essentially identical to the ones in get_loaded_extensions(). For this reason, most experienced extension writers tend to remove the confirm_rot13_compiled() function from their extensions - it is not necessary if you have no ambitions of getting your extension bundled with PHP.

The rot13 extension uses a special feature of the PHP language which allows strings to be built using single-quoted string literals with variables. This can be significantly faster than interpolating the strings in double quotes, as well as easier to audit for logic and security problems.

The pdo_mysql extension provides access to the MySQL database via the PHP Data Object (PDO) interface. This separation of functionality into a separate library makes it much easier to add support for new database vendors and APIs. The ftp extension provides full functionality for PHP to interact with file servers, including support for detailed access. The spl extension provides a number of standard interfaces and classes, such as a set of iterators, a class for generating random numbers, a standard set of exceptions, and a class to work with arrays. The spl_types extension helps developers make PHP a stronger typed language by providing a variety of class-based methods to handle different types such as int, float, bool, enum, and string.