如何使用config.php文件中的变量连接MySQLi？

I'm trying to make a MySQL & PHP based control panel for my community. And I've made a settings.php file with arrays with configs. I have class files for functions but there is MySQL function, which will not connect with data I've entered on settings.php..

I've tried other config file options, but none of them works...

on settings.php I have MySQL data like this:

$config['database']['host'] = "---"; 
$config['database']['user'] = "---";
$config['database']['password'] = "---";
$config['database']['database'] = "---";

And on userdata.php class file, where I'm trying to use those config variables I have:

$mysql = new mysqli($config['database']['host'], $config['database']['user'], $config['database']['password'], $config['database']['database']);

obviously, on userdata.php I have also required the settings.php..

I was expecting the output to be correct, but it shows only 'wrong MySQL data' errors...

I got it working with settings.php file like:

$config = array (
'db_host' => 'xxx',
'db_user' => 'xxx',
'db_pass' => 'xxx',
'db_database' => 'xxx'

and userdata.php like:

include 'settings.php';

$host = $config['db_host'];
$user = $config['db_user'];
$pass = $config['db_pass'];
$database = $config['db_database'];

$mysql = new mysqli($host, $user, $pass, $database);

you can try this way in connection.php file

<?php
include_once("path/config.php");

function OpenCon()
{
  $dbhost = $config['database']['host'];
  $dbuser = $config['database']['user'];
  $dbpass = $config['database']['password'];
  $db = $config['database']['db'];

  $conn = new mysqli($dbhost, $dbuser, $dbpass,$db) or die("Connect failed: %s
". 
  $conn -> error);

  return $conn;
}