Check for allow_url_include directive

"PHP will check to make sure that allow_url_fopen is enabled. If it is switched off, PHP will emit a warning and the fopen call will fail".

References in the PHP Manual:
* http://br2.php.net/manual/en/filesystem.configuration.php#ini.allow-url-include
* http://br2.php.net/manual/en/configure.about.php#configure.disable-url-fopen-wrapper
* http://br2.php.net/manual/en/features.remote-files.php
* http://br2.php.net/manual/en/wrappers.http.php
* http://br2.php.net/manual/en/function.fopen.php