Connection failed: SQLSTATE[HY000] [2002] No such file or directory

<br />
<b>Fatal error</b>:  Uncaught Error: Call to a member function query() on null in /home/desibutik/public_html/neoadmin/includes/comman_functions.php:331
Stack trace:
#0 /home/desibutik/public_html/includes/header.php(6): select_row('csetting', 'id=29')
#1 /home/desibutik/public_html/category.php(1): include('/home/desibutik...')
#2 {main}
  thrown in <b>/home/desibutik/public_html/neoadmin/includes/comman_functions.php</b> on line <b>331</b><br />