<?php

require_once 'includes/credentials.php';

class Mysql {
	private $conn;

	function __construct() {
		$this->conn = new mysqli(DB_SERVER, DB_USER, DB_PASSWORD, DB_NAME) or
					  die('There was a problem connecting to the database.');
	}

	function verify_Username_and_Pass($un, $pwd) {

		$query = "SELECT hs_memberID, password FROM hs_member WHERE hs_memberID = '$un';";

		if($stmt = $this->conn->prepare($query)) {
			$stmt->bind_param('ss', $un, $pwd);
			$stmt->execute();

			if($stmt->fetch()) {
				$stmt->close();
				return true;
			}
		}

	}
}

================== 2nd file

<?php

require 'Mysql.php';

class Membership {

	function validate_user($un, $pwd) {
		$mysql = New Mysql();
		$ensure_credentials = $mysql->verify_Username_and_Pass($un, md5($pwd));

		if($ensure_credentials) {
			$_SESSION['status'] = 'authorized';
			header("location: members.php");
		} else return "Please enter a correct username and password";

	}

	function log_User_Out() {
		if(isset($_SESSION['status'])) {
			unset($_SESSION['status']);

			if(isset($_COOKIE[session_name()]))
				setcookie(session_name(), '', time() - 1000);
				session_destroy();
		}
	}

	function confirm_Member() {
		session_start();
		if($_SESSION['status'] !='authorized') header("location: login.php");
	}

}