User cannot connect to server mysql Error. Please check includes/dbconnect.php

hello si am having have been using the softwae fo about 2 yeas suddenly 

i want to login today and i have the above eo

please help

Make sure your PHP version is 5.6 or below that, this script cannot work with higher versions. 

Also make sure your Database Username, Database name, and Database Password are correct also the DB user is connected with Database correctly.