Any.php

<?php

// assumes existence of 'config.php'
require_once 'config.php';

/**
 * Class Database
 */
class Database
{
    /**
     * @var mysqli
     */
    private $connection;

    /**
     * @var
     */
    public $some;

    /**
     * Database constructor.
     */
    function __construct()
    {
        // set connection: use global constants as defined in "config.php"
        $this->connection = new mysqli(db_host, db_user,db_password,'esl_parent');
        // catch error
        if($this->connection->connect_errno){
            // if the connection to the db did not work, maybe the database doesn't exist? Let's try
            $this->createDb();
        }

        // set public property
        $this->some = 'readable';

    }

    /**
     * Mock method
     */
    function createDb()
    {
        // your existing create db function
    }

    /**
     * Mock method 2
     */
    private function getMe()
    {
        // only work in current $this
    }

}

/*
 * About using classes
 * */

// creates an instance of "Database"
// $any now IS an instance of Database ...
$any = new Database();

// ... and can call all public methods & access public properties
// e.g. calling the createDb method
$any->createDb();

// or accessing public properties
echo $any->some;

// however, private methods & properties cannot be accessed
// $any->connection would fail
// $any->getMe() would fail

config.php

<?php
/*
 * Where ever this file is included/required,
 * the global constants will be available
 * e.g. 
 * // output: localhost!
 * echo db_host . '!'; 
 * 
 * */


// please set local variables

define('db_host', 'localhost');
define('db_user', 'root');
define('db_password', '');

install.php

<?php
/*
* Another option is to provide an installation script for your application
* Installation steps would usually be explained in a README.md file
*/

require 'databasescript.php';

$db = new objDatabaseConnetction();
$db->CreateDB();