What is the significance of the "open_basedir" restriction in PHP and how does it affect file inclusion?

The "open_basedir" restriction in PHP is a security feature that limits the files that can be accessed by PHP scripts to a specific directory or directories. This helps prevent unauthorized access to sensitive files on the server. When file inclusion functions like "include" or "require" are used, PHP checks if the target file is within the allowed directories specified in the "open_basedir" directive.

ini_set('open_basedir', '/path/to/allowed/directory');