Mysqli Singleton Class

mysql-singletone.php

<?php
/**
 * Created by AppzCoder.
 * User: SOHEL AMIN
 * Date: 10/30/2014
 * Time: 1:20 AM
 * URL: www.appzcoder.com
 */

class Database {
    // Database properties
    const DATABASE = '<DATABASE NAME>';
    const HOST = '<DATABASE HOST>';
    const DATABASE_USER = '<USER>';
    const DATABASE_PASSWORD = '<PASSWORD>';

    private $_mysqli;

    public function __construct()
    {
        $this->_mysqli = new mysqli(self::HOST, self::DATABASE_USER, self::DATABASE_PASSWORD, self::DATABASE);
        if ($this->_mysqli->connect_errno) {
            echo "Failed to connect to MySQL: (" . $this->_mysqli->connect_errno . ") " . $this->_mysqli->connect_error;
        }
    }

    public static function init()
    {
        static $instance = false;
        if( ! $instance ) {
            $instance = new self();
        }
        return $instance;
    }

    public function query($sql)
    {
        return $this->_mysqli->query($sql);
    }

}