Instantiating Singleton Pattern To Contain The Database Connection

[nodirtyrockstar]

I have multiple scripts referring to one another and it is getting a little confusing with database calls. I stumbled upon the singleton method, and I am trying to use it to create a Database class that will make sure there is only one connection at a time.

 

This is what I have:

class Database{
//Store the single instance of Database
private static $m_pInstance;
private function __construct(){
$mysqli = new mysqli($dbhost, $dbuser, $dbpass, $db);
 if ($mysqli->connect_error) {
	 die('Connect Error (' . $mysqli->connect_errno . ') '
			 . $mysqli->connect_error);
 }
}
public static function getInstance()
{
if(!self::$m_pInstance)
{
self::$m_pInstance = new Database();
}
return self::$m_pInstance;
}
}

 

My connection definitions are stored in a cfg.php file which is required by this script. For the most part I understand how this works, but not well enough to understand why it isn't working. Here is the reference to this database:

 

$mysqli = Database::getInstance();

 

Can someone help me figure out what I am doing wrong? The connection fails when I run it. It works when I put the above reference into a comment and simply connect with this:

 

$mysqli = new mysqli($dbhost, $dbuser, $dbpass, $db);
if ($mysqli->connect_error) {
   die('Connect Error (' . $mysqli->connect_errno . ') '
   . $mysqli->connect_error);
}

Thanks.

Edited October 4, 2012 by nodirtyrockstar

[nodirtyrockstar]

Well, I now see this is much more complex than I originally thought, and I am unable to edit or delete the first post...unless I am missing something. So please disregard.

[nodirtyrockstar]

I actually got it all to work, so I decided to post it in case someone comes across this thread.

 

I used the singleton pattern to extend mysqli. Here's my class:

 

class Database extends mysqli{
       private static $database;

       private function __construct(){
           global $dbhost, $dbuser, $dbpass, $db;
           parent::__construct($dbhost, $dbuser, $dbpass, $db);
           if ($this->connect_error) {
      		 die('Connect Error (' . $this->connect_errno . ') '
      				 . $this->connect_error);
      	 }
       }
       public static function getInstance()
       {
           if(!self::$database)
           {
               self::$database = new Database();
           }
           return self::$database;
       }
       public function __clone() {
           die(__CLASS__ . ' class can\'t be instantiated. Please use the method called getInstance.');
       }
   }

 

Then you can reference the class like so:

 

$mysqli = Database::getInstance();

[Christian F.]

This:

global $dbhost, $dbuser, $dbpass, $db;

is bad, at the very least use constants. Preferably you should be sending those details as (optional) parameters to the GetInstance () method, which then passes them on to the constructor.