index.php

<?php

    class DB {

        protected $db;
        private $_host;
        private $_user;
        private $_password;
        private $_database;

        function __construct($host,$username,$password,$database) {

            // set values in class for later usage
            $this->_host = $host;
            $this->_user = $username;
            $this->_password = $password;
            $this->_database = $database;

        }

        function connect() {

            $con = mysqli_connect($this->_host,$this->_user,$this->_password,$this->_database)or die("Can't connect, error log : ".mysqli_error());
            $this->_db = $con;
            return $con;
        }



    }