php操作mysql与sqlite类

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);
        $sql = 'SELECT COUNT(*) FROM '.$this->table($table).$condition;
        $result = $this->query($sql)->fetch();
        return $result['COUNT(*)'];
    }

    public function get_fields($table)
    {
        if ($this->config['type'] == 'mysql') {
            $sql = 'DESCRIBE '.$this->table($table);
            $key = 'Field';
        } else if ($this->config['type'] == 'sqlite') {
            $sql = 'PRAGMA table_info('.$this->table($table).')';
            $key = 'name';
        }
        $fields = $this->query($sql)->fetchall();
        foreach ($fields as $value) {
            $result[] = $value[$key];
        }
        return $result;
    }

    public function insert($table, $array)
    {
        if (!is_array($array)) {
            return false;
        }
        foreach ($array as $key => $value) {
            $cols[] = $key;
            $vals[] = '\''.$this->strescape($value).'\'';
        }
        $col = join(',', $cols);
        $val = join(',', $vals);
        $sql = 'INSERT INTO '.$this->table($table).' ('.$col.') VALUES ('.$val.')';
        return $this->exec($sql);
    }

    public function update($table, $array, $condition)
    {
        if (!is_array($array)) {
            return false;
        }
        $condition = $this->format_condition($condition);
        foreach ($array as $key => $value) {
            $vals[] = $key.' = \''.$this->strescape($value).'\'';
        }
        $values = join(',', $vals);
        $sql = 'UPDATE '.$this->table($table).' SET '.$values.$condition;
        return $this->exec($sql);
    }

    public function delete($table, $condition)
    {
        $condition = $this->format_condition($condition);
        $sql = 'DELETE FROM '.$this->table($table).$condition;
        return $this->exec($sql);
    }
}

//例子
$db = new db();
//配置数据库，2选一
//$db->mysql($host, $user, $password, $dbname, '表前缀', 'GBK');
$db->sqlite('d:\Backup\test2.db');

//SQL语句查询
$db->query('SELECT * FROM 表')->fetch();//或者fetchall();

//执行一条无返回结果的SQL语句，如插入数据
$db->exec($sql);

//返回最后插入的数据主键
echo $db->lastinsertid();

/***** 下面的操作如果条件为数组则不需要字符转义 *****/

//查询一条数据
$db->fetch('表', '字段1,字段2', '条件，可用数组，如：array(id => 1)', 'id DESC');

//查询所有数据
$db->fetchall('表', '字段1,字段2', '条件，可用数组', 'id DESC', '显示条数');

//插入一条数据
$db->insert('test', array('username' => 'lxx', 'password' => 'lxx'));

//更新一条数据
$db->update('表', array('字段' => '值', '字段2' => '值'), array('id' => '1 更新ID为1的数据'));

//删除一条数据
$db->delete('test', array('username' => 'lxx'));