How to use the instance of DB class inside functions? - php

Question

This is my DB class. (DB.php)
<?php
class DB {
protected $db_name = "data_db";
protected $db_user = "root";
protected $db_pass = "root";
protected $db_host = "localhost";
public function __construct() {
$this->mysqli = new mysqli($this->db_host, $this->db_user, $this->db_pass, $this->db_name);
}
public function __destruct() {
$this->mysqli->close();
}
}
?>
This is my users.php file.
<?php
require_once "core/DB.php";
function user_data() {
global $db;
$db = new DB();
$data = array();
$session_user_id = $_SESSION["user_id"];
$data_row = $db->mysqli->query("SELECT * FROM `users` WHERE `user_id` = '$session_user_id'");
$data = $data_row->fetch_assoc();
return $data;
}
?>
How can I use the $db instance of DB class inside my functions?
Should I call the instance only once and than make it a global variable to use in all functions?

Answer 1

pleeeeaaase, don't use global variables
try it with a singleton pattern
class DB {
protected $db_name = "data_db";
protected $db_user = "root";
protected $db_pass = "root";
protected $db_host = "localhost";
public static function getInstance()
{
static $instance = null;
if (is_null($instance)) {
$instance = new DB();
}
return $instance;
}
public function __construct() {
$this->mysqli = new mysqli($this->db_host, $this->db_user, $this->db_pass, $this->db_name);
}
public function __destruct() {
$this->mysqli->close();
}
}
in your functions you can use it than this way
function user_data() {
$db = DB::getInstance();
$data = array();
$session_user_id = $_SESSION["user_id"];
$data_row = $db->mysqli->query("SELECT * FROM `users` WHERE `user_id` = '$session_user_id'");
$data = $data_row->fetch_assoc();
return $data;
}
just call DB::getInstance() to get all time the same instance of your class