As long as allow_url_fopen is enabled in php.ini, you can use HTTP and FTP URLs with most of the functions that take a filename as a parameter. In addition, URLs can be used with the include(), include_once(), require() and require_once() statements.
Note: In PHP 4.0.3 and older, in order to use URL wrappers, you were required to configure PHP using the configure option --enable-url-fopen-wrapper.
For example, you can use this to open a file on a remote web server, parse the output for the data you want, and then use that data in a database query, or simply to output it in a style matching the rest of your website.
Example 21-1. Getting the title of a remote page
You can also write to files on an FTP server (provided that you have connected as a user with the correct access rights). You can only create new files using this method; if you try to overwrite a file that already exists, the fopen() will fail.
To connect as a user other than 'anonymous', you need to specify the username (and possibly password) within the URL, such as 'ftp://user:email@example.com/path/to/file'. (You can use the same sort of syntax to access files via HTTP when they require Basic authentication.)