Error Message Directory Theme

I currently have the website directory theme active for my current business but I am now seeing this error message every time someone tries to submit a listing on to the directory.

Warning: mysql_real_escape_string(): Can’t connect to local MySQL server through socket ‘/var/lib/mysql/mysql.sock’ (2) in /var/sites/y/yourlocalbury.co.uk/public_html/bury-business-directory/wp-content/themes/directorypress/PPT/func/funcs_premiumpress.php on line 695

Warning: mysql_real_escape_string(): A link to the server could not be established in /var/sites/y/yourlocalbury.co.uk/public_html/bury-business-directory/wp-content/themes/directorypress/PPT/func/funcs_premiumpress.php on line 695

I have updated the plugins and WordPress as suggested by the person who created the site initially but this hasn’t worked. Can anyone advise???

Thanks