error_reporting(E_ALL);
ini_set('display_errors', 1);

<br />
<b>Fatal error</b>:  Uncaught mysqli_sql_exception: Access denied for user 'u301570038_demo_db'@'localhost' (using password: YES) in /home/u301570038/domains/khayatisystem.io/public_html/demo/config/db.php:21
Stack trace:
#0 /home/u301570038/domains/khayatisystem.io/public_html/demo/config/db.php(21): mysqli_connect()
#1 /home/u301570038/domains/khayatisystem.io/public_html/demo/index.php(4): require_once('/home/u30157003...')
#2 {main}
  thrown in <b>/home/u301570038/domains/khayatisystem.io/public_html/demo/config/db.php</b> on line <b>21</b><br />