The behaviour of these functions is affected by settings in php.ini.
|allow_url_include||"0"||PHP_INI_SYSTEM||Available since PHP 5.2.0.|
|sys_temp_dir||""||PHP_INI_SYSTEM||Available since PHP 5.5.0.|
Here's a short explanation of the configuration directives.
This option enables the URL-aware fopen wrappers that enable accessing URL object like files. Default wrappers are provided for the access of remote files using the ftp or http protocol, some extensions like zlib may register additional wrappers.
This setting requires allow_url_fopen to be on.
Define the user agent for PHP to send.
Default timeout (in seconds) for socket based streams.
The email address to be used on unauthenticated FTP connections and as the value of From header for HTTP connections, when using the ftp and http wrappers, respectively.
This enables PHP to interoperate with Macintosh systems, but defaults to Off, as there is a very small performance penalty when detecting the EOL conventions for the first line, and also because people using carriage-returns as item separators under Unix systems would experience non-backwards-compatible behaviour.