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

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<b>Fatal error</b>:  Uncaught Error: Call to a member function query() on null in /home/syscomperipheral/public_html/neoadmin/includes/comman_functions.php:283
Stack trace:
#0 /home/syscomperipheral/public_html/includes/header.php(46): insert_row('device_ip', Array)
#1 /home/syscomperipheral/public_html/productlist.php(1): include('/home/syscomper...')
#2 {main}
  thrown in <b>/home/syscomperipheral/public_html/neoadmin/includes/comman_functions.php</b> on line <b>283</b><br />