php操作mysql与sqlite类
来源：http://www.yytweb.com/?s=article-13.html
源博客上的类，有些小问题(表前缀只对mysql进行了处理，sqlite的没有处理)，下面的这个是我做过一些处理之后的类，我也测试过了，可以使用。感兴趣的朋友也可以继续扩展下。

<?php
/**
 * 文件描述  PDO数据库操作类
 * =================================================================
 * 作    者  YYT<gyyst@126.com>
 * =================================================================
 */

class db
{
	private $config;

	private $db;

	public $querynum;

	public function mysql($host, $user, $password, $dbname, $tablepre = '', $charset = 'GBK')
	{
		$this->config['type'] = 'mysql';
		$this->config['tablepre'] = $tablepre;
		$this->config['mysql']['host'] = $host;
		$this->config['mysql']['user'] = $user;
		$this->config['mysql']['password'] = $password;
		$this->config['mysql']['dbname'] = $dbname;
		$this->config['mysql']['charset'] = $charset;
	}

	public function sqlite($datafile,$tablepre = '')
	{
		$this->config['type'] = 'sqlite';
		$this->config['sqlite']['file'] = $datafile;
                $this->config['tablepre'] = $tablepre;
	}

	private function connect()
	{
		if (isset($this->db)) {
			return true;
		}
		if ($this->config['type'] == 'mysql') {
			try{
				$this->db = new PDO('mysql:host='.$this->config['mysql']['host'].';dbname='.$this->config['mysql']['dbname'], $this->config['mysql']['user'], $this->config['mysql']['password'], array(PDO::ATTR_PERSISTENT => true));
				$this->db->query('SET NAMES '.$this->config['mysql']['charset']);
			} catch (PDOException $e) {
				exit('数据库连接失败：'.$e->getMessage());
			}
		}
		if ($this->config['type'] == 'sqlite') {
			!file_exists($this->config['sqlite']['file']) && exit('没有找到SQLITE数据库');
			$this->db = new PDO('sqlite:'.$this->config['sqlite']['file']);
		}
		!isset($this->db) && exit('不支持该数据库类型 '.$this->config['type']);
	}

	public function table($table)
	{
		return '`'.$this->config['tablepre'].$table.'`';		
	}

	public function strescape($str)
	{
		if ($this->config['type'] === 'mysql') {
			return !get_magic_quotes_gpc() ? addslashes($str) : $str;
		}
		if ($this->config['type'] === 'sqlite') {
			return str_replace('\'', '\'\'', $str);
		}
		return $str;
	}

	public function format_condition($condition)
	{
		if (is_array($condition)) {
			foreach ($condition as $key => $value) {
				$join[] = $key.' = \''.$this->strescape($value).'\'';
			}
			return ' WHERE '.join(' AND ', $join);
		}
		return $condition ? ' WHERE '.$condition : '';
	}

	private function error()
	{
		if ($this->db->errorCode() != '00000') {
			$error = $this->db->errorInfo();
			exit('SQL语句错误：'.$error['2']);
		}
	}

	public function query($sql)
	{
		$this->connect();
		$result = $this->db->query($sql);
		$this->error();
		$result->setFetchMode(PDO::FETCH_ASSOC);
		$this->querynum++;
		return $result;
	}

	public function exec($sql)
	{
		$this->connect();
		$result = $this->db->exec($sql);
		$this->error();
		$this->querynum++;
		return $result;
	}

	public function lastinsertid()
	{
		return $this->db->lastInsertId();
	}

	public function fetchall($table, $field, $condition = '', $sort = '', $limit = '')
	{
		$condition = $this->format_condition($condition);
		$sort && $sort = ' ORDER BY '.$sort;
		$limit && $limit = ' LIMIT '.$limit;
		$sql = 'SELECT '.$field.' FROM '.$this->table($table).$condition.$sort.$limit;
		return $this->query($sql)->fetchall();
	}

	public function fetch($table, $field, $condition = '', $sort = '')
	{
		$condition = $this->format_condition($condition);
		$sort && $sort = ' ORDER BY '.$sort;
		$sql = 'SELECT '.$field.' FROM '.$this->table($table).$condition.$sort.' LIMIT 1';
		return $this->query($sql)->fetch();
	}

	public function rowcount($table, $condition = '')
	{
		$condition = $this->format_condition($condition);
		$sql = 'SELECT CO