How to instantiate mysqli in class

[Fmdpa]

I am creating a User's class, and several methods require a database connection. Instead of instantiating mysqli in each method that needs it, how would I instantiate it for public access?I tried this:

class User {   __construct() {	  require_once 'db.php';	  public $db;  }//methods}

where db.php is:

define('HOST', 'localhost');define('USER','root');define('PASS','');define('DB','database');$db = new mysqli(HOST,USER,PASS,DB);

with no success. The error it gave me was caused by stating the scope of $db.

[boen_robot]

It will be easiest if you add the connection as an argument to the constructor, but you could also create a static method that you call, and modify a static property from within it, like:

class Db {	private static connection;	public const HOST = 'localhost';	public const USER = 'root';	public const PASS = '';	public const DATABASE = 'database';	public static getInstance() {		if (is_object(self::$connection)) {			return self::$connection;		}else {			return self::$connection = new mysqli(self::HOST, self::USER, self::PASS, self::DATABASE);		}	}}class User {	protected db;	__construct() {		$this->db = Db::getInstance();	}	//methods}

[Fmdpa]

"Unexpected T_VARIABLE on Line 3" (private static connection;)When you define the scope of a property, must you preface it with the $ sign? Also, I'm having trouble understanding this:

if (is_object(self::$connection)) {	 return self::$connection;}

Is that checking if the $connection object is already instantiated? If so, we didn't get to the line that instantiates it, yet, so why would it be?

[Synook]

Yes, all variables need to be prefixed with $. The condition is so that the first time Db::getInstance() is called, the MySQL-i instance is created. Then on future calls, the existing object is used (because, as a class variable, it already exists).

[Fmdpa]

Ok, I just assumed that the object was recreated each time the script ran. So I should make it like this:

class Db {	private static $connection; //change no. 1	public const HOST = 'localhost';	public const USER = 'root';	public const PASS = '';	public const DATABASE = 'database';	public static getInstance() {		if (is_object(self::$connection)) {			return self::$connection;		}else {			return self::$connection = new mysqli(self::HOST, self::USER, self::PASS, self::DATABASE);		}	}}class User {	protected $db; //change #2	__construct() {		$this->db = Db::getInstance();	}	//methods}

[boen_robot]

I've been coding too much C# lately it seems .