Syntax - accessing a class's property's method - php

Question

I just upgraded my php form mysql to use mysqli in an object oriented approach. I have reason to believe that this code has bug in it. My goal is to use a singlton pattern to guarantee only one database connection per script execution. $db holds the database link.
Can someone verify the line
return $one->$db->query($query);
the syntax looks off.
class one
{
private static $single = NULL;
public $db = NULL;
public function __construct()
{
$this->db = new mysqli(DB_HOST, DB_USER, DB_PASS, DB_DATABASE);
self::$single=1;
}
public static function make_one()
{
if(self::$single==NULL)
{
return new self();
}
}
}
/*database*/
class database
{
public function __construct()
{
one::make_one();
}
public static function arche_query($query)
{
return $one->$db->query($query);
}
}

Answer 1

Change it to
return one::make_one->db->query($query);
how ever your singleton pattern is not correct
A singleton pattern should create only one instance , in your case its not that case
class one
{
private static $_selfInstace;
public $db;// default is null so no need to assign
public function __construct()
{
$this->db = new mysqli(DB_HOST, DB_USER, DB_PASS, DB_DATABASE);
}
public static function getInstance()
{
if( !(self::$_selfInstace instanceof self) ) {
self::$_selfInstace= new self();
}
return self::$_selfInstace;
}
}
class database
{
public function __construct()
{
}
public static function arche_query($query)
{
return one::getInstance()->db->query($query);
}
}