Warning: Use of undefined constant DIR - assumed 'DIR' (this will throw an Error in a future version of PHP) in /wordpress/index.php on line 13

Warning: require(DIR/wp-blog-header.php): failed to open stream: No such file or directory in /wordpress/index.php on line 13

Fatal error: require(): Failed opening required 'DIR/wp-blog-header.php' (include_path='.:/usr/local/lib/php') in /wordpress/index.php on line 13