Simple Database class

db.php

<?php
/**
 * Simple database class
 * (c) 2012
 * Author: Giel Berkers
 * Date: 5-3-12
 * Time: 14:24
 */

class Db
{
    /**
     * @var PDO
     */
    private $pdo;

    private static $instance;

    private function __construct(){}

    private function instance()
    {
        if(!self::$instance) {
            self::$instance = new Db();
        }
        return self::$instance;
    }

    /**
     * Connect to database
     * @param $database
     * @param $username
     * @param $password
     * @param string $host
     */
    public static function connect($database, $username, $password, $host = 'localhost')
    {
        self::instance()->pdo = new PDO('mysql:host=' . $host . ';dbname=' . $database, $username, $password);
    }

    /**
     * Run a query
     * @param $sql
     * @param int $fetchStyle
     * @return resource
     */
    public static function mq($sql, $fetchStyle = PDO::FETCH_ASSOC) {
        $result = self::instance()->pdo->query($sql)->fetch($fetchStyle);
        return $result;
    }

    /**
     * @param $sql
     * @return PDOStatement
     */
    public static function sql($sql) {
        $result = self::instance()->pdo->query($sql);
        return $result;
    }

    /**
     * Get an associated array
     * @param $sql
     * @return array
     */
    public static function ma($sql) {
        $result = self::instance()->mq($sql);
        return $result[0];
    }

    /**
     * Get a single result
     * @param $sql
     * @return mixed
     */
    public static function sr($sql) {
        $result = self::instance()->pdo->query($sql)->fetchColumn(0);
        return $result;
    }

    /**
     * Insert or update automatically if the key/value check exists or not
     * @param $key
     * @param $value
     * @param array $values
     * @param $table
     */
    public static function insertOrUpdate($key, $value, $values = array(), $table)
    {
        if(!empty($key) && !empty($values))
        {
            if(self::sr(
                sprintf('SELECT COUNT(*) AS total FROM %1$s WHERE %2$s = \'%3$s\';',
                    $table, $key, $value)
            ) >= 1) {
                // Update
                $statements = array();
                foreach($values as $k => $v) {
                    $statements[] = $k . ' = \''. $v .'\'';
                }
                self::mq(
                    sprintf('UPDATE %1$s SET %2$s WHERE %3$s = \'%4$s\';',
                        $table, implode(',', $statements), $key, $value)
                );
            } else {
                // New
                self::mq(
                    sprintf('INSERT INTO %1$s (%2$s) VALUES (\'%3$s\');',
                        $table, implode(',', array_keys($values)), implode('\', \'', $values))
                );
            }
        }
    }
}