PHP OOP Database class using PDO and Singleton pattern. Only one instance of the class will be made, this requires less memory.

class.database.php

<?php
/*
* Mysql database class - only one connection alowed
*/
<?php

    class DB {
      private $connection;
      private static $_instance;

      private $dbhost = "localhost"; // Ip Address of database if external connection.
      private $dbuser = "root"; // Username for DB
      private $dbpass = "root"; // Password for DB
      private $dbname = "root"; // DB Name

      /*
      Get an instance of the Database
      @return Instance
      */	
      public static function getInstance(){
        if(!self::$_instance) {
              self::$_instance = new self();
           }
          return self::$_instance;
        }

      // Constructor
      private function __construct() {
        try{
        $this->connection = new PDO('mysql:host='.$this->dbhost.';dbname='.$this->dbname, $this->dbuser, $this->dbpass);
        $this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
 	
	// Error handling
        }catch(PDOException $e){
          die("Failed to connect to DB: ". $e->getMessage());
        }
      }

      // Magic method clone is empty to prevent duplication of connection
      private function __clone(){}
      
      // Get the connection	
      public function getConnection(){
        return $this->connection;
      }
    }

$db = DB::getInstance();
$conn = $db->getConnection();

?>