Creating a globally accessible MySQLi object

Question

I have multiple classes that use static methods. These functions connect to the database using

$mysqli = new mysqli(DB_SERVER, DB_USER, DB_PASS, DB_NAME);

where the constants DB_SERVER, DB_USER, DB_PASS, DB_NAME are database variables defined in a globally accessible file. Recently, my site started becoming slow and after profiling the script I realized that the call to create the object($mysqli) was causing this problem.

Most of my classes extend from mysqli such that

public function __construct($user_id) {
    parent::__construct(DB_SERVER, DB_USER, DB_PASS, DB_NAME);
    $this->retrieve_user_details($user_id);
    $this->check_user_account_type();

}

It is to my understanding that static methods DO NOT use the __construct method.

Could someone guide me on how I can create the $mysqli object once such that it can be accessed by all static methods that require it.

Answer 1

Here is one approach:

Create a singleton class, that can be accessed statically from anywhere.

class DBConnector {
    private static $instance ;
    public function __construct($host, $user, $password, $db){
      if (self::$instance){
        exit("Instance on DBConnection already exists.") ;
      }
    }

    public static function getInstance(){
      if (!self::$instance){
        self::$instance = new DBConnector(a,b,c,d) ;
      }
      return $instance ;
    }
}

An example would be:

$mysqli = DBConnector::getInstance() ;

Hovewer I suggest using another solution as well:

$mysqli = new MySQLi(a,b,c,d) ;

Then you could pass that object to other classes (constructor)

class Shop {
  private $mysqli ;
  public function __construct(MySQLi $mysqli){
    $this->mysqli = $mysqli ;
  }
}

$show = new Shop($mysqli) ;

Answer 2

To elaborate on a mysqli singleton:

define('SERVER', 'localhost');
define('USERNAME', 'root');
define('PASSWORD', 'password');
define('DATABASE', 'databaseName');

class mysqliSingleton
{
    private static $instance;
    private $connection;

    private function __construct()
    {
        $this->connection = new mysqli(SERVER,USERNAME,PASSWORD,DATABASE);
    }

    public static function init()
    {
        if(is_null(self::$instance))
        {
            self::$instance = new mysqliSingleton();
        }

        return self::$instance;
    }


    public function __call($name, $args)
    {
        if(method_exists($this->connection, $name))
        {
             return call_user_func_array(array($this->connection, $name), $args);
        } else {
             trigger_error('Unknown Method ' . $name . '()', E_USER_WARNING);
             return false;
        }
    }
}

You can then request the database connection by calling:

$db = mysqliSingleton::init();

You can then retrieve the database connection in your own objects:

class yourClass
{
    protected $db;

    public function __construct()
    {
        $this->db = mysqliSingleton::init();
    }
}