In order to use these functions, you must compile PHP with the --enable-overload option. Starting with PHP 4.3.0 this extension is enabled by default. You can disable overload support with --disable--overload .
The Windows version of PHP has built-in support for this extension. You do not need to load any additional extensions in order to use these functions.
Note: Builtin support for overload is available with PHP 4.3.0.