A wrapper is additional code which tells the stream how to handle specific protocols / encodings.
A wrapper is additional code which tells the stream how to handle specific protocols/encodings. For example, the http wrapper knows how to translate a URL into an HTTP/1.0 request for a file on a remote server. There are many wrappers built into PHP by default (See 付録I), and additional, custom wrappers may be added either within a PHP script using stream_register_wrapper(), or directly from an extension using the API Reference in 第43章. Because any variety of wrapper may be added to PHP, there is no set limit on what can be done with them. To access the list of currently registered wrappers, use stream_get_wrappers().