<?php

class Core
{
    public $dbh;   // database connection handle
    private static $dsn  = 'mysql:hostname=;dbname=dbname';
    private static $user = 'user';
    private static $pass = 'pass';
     private static $instance;


    public function __construct () {
      $this->dbh = new PDO(self::$dsn,self::$user,self::$pass);
    }

    public static function getInstance(){
        if(!isset(self::$instance)){
            $object= __CLASS__;
            self::$instance=new $object;
        }
        return self::$instance;
    }

}