Model

<?php

class Model {

    private static $_instance = null;
    private $db;

    private function __construct() {
        try {
            $this->db = new PDO('mysql:host='. Config::get('mysql/host') .';dbname='. Config::get('mysql/dbname'), Config::get('mysql/user'), Config::get('mysql/pass'));
        } catch(PDOException $e) {
            die($e->getMessage());
        }
    }

    static function getInstance() {
        if(!isset(self::$_instance)) {
            self::$_instance = new Model();
        }
        return self::$_instance;
    }

    function unique($item, $table, $item_value) {
        $sql = "SELECT {$item} FROM {$table} WHERE {$item} = {$item_value}";
        $result = $this->db->query($sql);
        if($result->rowCount() === 0) {
            return true;
        } else {
            return false;
        }
    }

}