Database

<?php

class Database {
    private static $db = "dbName";
    private static $host = "host";
    private static $username = "";
    private static $password = "";

    private static $conn = null;

    public function __construct(){
        die("Initialization is not allowed");
    }

    public static function connect(){
        if(null == self::$conn){
            try {
                self::$conn = new PDO("mysql:host=".self::$host.";"."dbname=".self::$db, self::$username, self::$password);
                self::$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            } catch(PDOException $e){
                echo "Connection failed " . $e->getMessage();
            }
        }
        return self::$conn;
    }

    public static function disconnect(){
        self::$conn = null;
    }
}