open_basedir

The open_basedir directive limits access to files in a list of provided directories, and their nested directories. That directive can only be set in the php.ini.

Functions such as fopen(), file_get_contents, file_put_contents, curl_get() when working on local files, zip_open(), etc. are affected.

Documentation

See also What is open_basedir in PHP and How to Configure It Securely.

Related : include_path, php.ini, .htaccess