Registry Pattern Example

tim.php

<?php
class Registry {
    private $registry = array();
    private static $instance = null;

    public static function getInstance() {
        if($this->instance === null) {
            $this->instance = new Registry();
        }

        return $this->instance;
    }

    private function __construct() {}
    private function __clone() {}

    public function set($key, $value) {
        if (isset($this->registry[$key])) {
            throw new Exception("There is already an entry for key " . $key);
        }
        $this->registry[$key] = $value;
    }

    public function get($key) {
        if (!isset($this->registry[$key])) {
            throw new Exception("There is no entry for key " . $key);
        }
        return $this->registry[$key];
    }
}


$mysqli = new mysqli();
$mysqli->connect('localhost', 'luminusm', 'NiX8VWe5', 'luminusm_tedesco');

$registry = Registry::getInstance();
$registry->set('mysqli', $mysqli);

can u please writing the comments of ur codes