browsergame/libs/UserDataCache.php

<?php
class UserDataCache {
	public static function getInstance() {
		return new UserDataCache(new mysqli(DB_HOST, DB_USER, DB_PASS, DATABASE));
	}
	private $db;
	private function __construct(mysqli $db) {
		$this->db = $db;
	}
	public function getUserById($userId) {
	}
	public function getUserByLogin($email, $password) {
		$sql = sprintf("SELECT user_id FROM users WHERE email = '%s' AND password = md5('%s') LIMIT 1", $email, $password);
		$result = $this->db->query($sql);
		if(!$result) {
			return false;
		}
		
		$userData = $result->fetch_assoc();
		return $userData;
	}
}