// connect_mysql.php
<?php

	define("DB_HOST", "localhost");
	define("DB_USER", "user");
	define("DB_PASS", "pass");
	define("DB_DB", "_notify");

	$dbc = new mysqli(DB_HOST, DB_USER, DB_PASS, DB_DB);

	if (!$dbc) {
		die('Cannot connect to database: ' . $dbc->error);
	}
?>

// index.php
<?php

	include('./connect_mysql.php');

	class Login {

		public $user;
		private $pass;
		private $_authCode;

		public function __construct($user, $password) {
			$this->user = $user;
			$this->pass = $password;
			$this->_authCode = -1;
		}

		public function authCode() {
			return $this->_authCode;
		}
		public function authenticate() {
			$q = "SELECT username, password  FROM users";
			$r = $dbc->query($q);

			while ($check = $r->fetch_object()) {
				if ($user == $check->username) {
					if (trim(md5('$password')) == $check->password) {
						$this->_authCode = 1;
						break;
					}
					else {
						$this->_authCode = 0;
						break;
					}
				}
			}
		}
	}
?>