View file includes/classes/DB.php

<?php
// ---------------------------- Класс для работы с базами данных -------------------------------//
class PDO_ extends PDO {
	static $counter = 0;

	function __construct($dsn, $username, $password) {
		parent::__construct($dsn, $username, $password);
		$this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
		$this->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
		$this->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true);
	}

	function prepare($sql, $params = array()) {
		$stmt = parent::prepare($sql, array(
				PDO::ATTR_STATEMENT_CLASS => array('PDOStatement_')
				));
		return $stmt;
	}

	function query($sql, $params = array()) {
		self::$counter++;
		$stmt = $this->prepare($sql);
		$stmt->execute($params);
		return $stmt;
	}

	function querySingle($sql, $params = array()) {
		$stmt = $this->query($sql, $params);
		return $stmt->fetchColumn(0);
	}

	function queryFetch($sql, $params = array()) {
		$stmt = $this->query($sql, $params);
		return $stmt->fetch();
	}

	function queryCounter() {
		return self::$counter;
	}
}
// ----------------------------------------------------//
class PDOStatement_ extends PDOStatement {
	function execute($params = array()) {
		if (func_num_args() == 1) {
			$params = func_get_arg(0);
		} else {
			$params = func_get_args();
		}
		if (! is_array($params)) {
			$params = array($params);
		}
		parent::execute($params);
		return $this;
	}

	function fetchSingle() {
		return $this->fetchColumn(0);
	}

	function fetchAssoc() {
		$this->setFetchMode(PDO::FETCH_NUM);
		$data = array();
		while ($row = $this->fetch()) {
			$data[$row[0]] = $row[1];
		}
		return $data;
	}
}

// --------------- Класс singleton для подключения к БД -----------------//
class DB {
	private static $instance;
	private function __construct() {}
	private function __clone() {}

	public static function run() {

		if (! isset(self::$instance)) {

			try {
				self::$instance = new PDO_('mysql:host='.DBHOST.';port='.DBPORT.';dbname='.DBNAME, DBUSER, DBPASS);
				self::$instance->exec('SET CHARACTER SET utf8');
				self::$instance->exec('SET NAMES utf8');
			}

			catch (PDOException $e) {
				if (file_exists(BASEDIR.'/install/index.php')) {
					header ('Location: /install/index.php');
					exit;
				}
				die('Connection failed: '.$e->getMessage());
			}
		}
		return self::$instance;
	}

	final public function __destruct() {
		self::$instance = null;
	}
}