Fatal error: Class 'mysqli' not found

installed the plugin and used it tonight but came up with this error:

Successfully created task with undo option

Fatal error: Class ‘mysqli’ not found in /home/wwwchri/public_html/wp-content/plugins/safe-search-replace/Ssr/TaskExecuter.php on line 6

any ideas are appreciated ??

https://www.ads-software.com/plugins/safe-search-replace/