CODEWITHSUNDEEP
phpmysqloopmysqli
Vidhya Kumar
Vidhya Kumar

Reputation: 128

Static Method vs Static Instances

Consider the following code below, I've been thought by Lynda.com to create a database class like this, my question is why not create a static method for the database entirely instead of storing an instance into a static property?

<?php
class Database {

  private $conn;
  private static $init;

  public function __construct() {
     $this->conn = new mysqli('localhost','root','root','mydb');
  }

  public static function getInstance() {
     self::$init = new self();
     return self::$init;
  }

}

$db = Database::getInstance();

?>

Upvotes: 2

Views: 139

Answers (3)

Nikita Melnikov
Nikita Melnikov

Reputation: 209

If you want to use singleton you should to protect __construct()

class DB
{
  private static $instance;

  private function __construct($args)
  {
    // do some
  }

  public static function getInstance()
  {
    // get instance
  }
}

$query = 'SELECT etc...';
$stmt = DB::getInstance()->prepare($query);

I use this pattern in DB class. But if you have more than 1 connection you should NOT! use singleton.

Upvotes: 2

goat
goat

Reputation: 31813

My guess is that code you posted was intended to be the following because it looks like it was intended to be a singleton. I've only changed the getInstance() method.

class Database {

  private $conn;
  private static $init;

  public function __construct() {
     $this->conn = new mysqli('localhost','root','root','mydb');
  }

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

}

$db = Database::getInstance();

I think this should clear up the confusion of why a static instance variable is used.

If this wasn't intended to be a singleton, then your question of "why didn't they just use a static method" should have the answer "they should have".

Upvotes: 1

Manny Ramirez
Manny Ramirez

Reputation: 148

Just to clarify, $db is a Database object, which is instantiated by calling static method getInstance().

why not create a static method for the database entirely?

A static method is defined inside a class, however it can be called without having to instantiate the class. In other words, a static method belongs to the class, since in can be called without instantiating an object.

You can add methods to the Database class to interact with the database as you deem necessary.

Upvotes: 0

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