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.