error in require_once include_path = 'C: \ xampp \ php \ PEAR'

What is this error:

  

Warning: require_once (../ config.php): failed to open stream: No such file or directory in C: \ xampp \ htdocs ... \ CRUD.php on line 2

     

Fatal error: require_once (): Failed opening required '../config.php' (include_path = 'C: \ xampp \ php \ PEAR') in C: \ xampp \ htdocs ... \ CRUD.php on line 2

Note: The file config.php exists, and is in a folder that is being called require .