<?php

class DB extends PDO {
    private $_host = 'localhost',
        $_database = 'roystonvasey',
        $_username = 'root',
        $_password = '',
        $_tablePrefix = 'rv_',
        $_charset = 'utf8';

    private function __construct() {
        $dsn = 'mysql:dbname=' . $this->_database . ';host=' . $this->_host;
        parent::__construct($dsn, $this->_username, $this->_password);
        $this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        $this->exec("SET NAMES {$this->_charset}");
     }

    static function getInstance() {
        static $db;
        if ($db == null) {
            $db = new self;
        }
        return $db;
     }

     function addTablePrefix($table_name) {
        return '`' . $this->_tablePrefix . $table_name . '`';
     }

     function insert($table_name, $data) {
        $sql = 'INSERT INTO ' . $this->addTablePrefix($table_name);
        $aux = array_values($data);
        if ($aux != $data) {
            $sql .= ' (`' . implode('`, `', array_keys($data)) . '`)';
        }
        $sql .= ' VALUES(' . implode(', ', array_fill(0, count($aux), '?')) . ')';
        $stmt = $this->prepare($sql);
        $stmt->execute($val);
        return $this->lastInsertId();
    }

    function update($table_name, $data, $id) {
        $items = array();
        foreach (array_keys($data) as $v) {
            $items[] = "`$v`=?";
        }
        $items = implode(',', $items);
        $sql = "UPDATE {$this->addTablePrefix($table_name)} SET $items WHERE `id`=" . intval($id);
        $stmt = $this->prepare($sql);
        $stmt->execute(array_values($data));
        return $stmt->rowCount();
    }

    function delete($table_name, $id) {
        $sql = "DELETE FROM {$this->addTablePrefix($table_name)} WHERE `id`=" . intval($id);
        $stmt = $this->query($sql);
        return $stmt->rowCount();
    }
}