<?php//数据库连接类，不建议直接使用DB，而是对DB封装一层//这个类不会被污染，不会被直接调用class DB {    //pdo对象    private $_pdo = null;    //用于存放实例化的对象    static private $_instance = null;        //公共静态方法获取实例化的对象    static protected function getInstance() {        if (!(self::$_instance instanceof self)) {            self::$_instance = new self();        }        return self::$_instance;    }        //私有克隆    private function __clone() {}        //私有构造    private function __construct() {        try {            $this->_pdo = new PDO(DB_DNS, DB_USER, DB_PASS, array(PDO::MYSQL_ATTR_INIT_COMMAND=>‘SET NAMES ‘.DB_CHARSET));            $this->_pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);        } catch (PDOException $e) {            exit($e->getMessage());        }    }        //新增    protected function add($_tables, Array $_addData) {        $_addFields = array();        $_addValues = array();        foreach ($_addData as $_key=>$_value) {            $_addFields[] = $_key;            $_addValues[] = $_value;        }        $_addFields = implode(‘,‘, $_addFields);        $_addValues = implode("‘,‘", $_addValues);        $_sql = "INSERT INTO $_tables[0] ($_addFields) VALUES (‘$_addValues‘)";        return $this->execute($_sql)->rowCount();    }        //修改    protected function update($_tables, Array $_param, Array $_updateData) {        $_where = $_setData = ‘‘;        foreach ($_param as $_key=>$_value) {            $_where .= $_value.‘ AND ‘;        }        $_where = ‘WHERE ‘.substr($_where, 0, -4);        foreach ($_updateData as $_key=>$_value) {            if (Validate::isArray($_value)) {                $_setData .= "$_key=$_value[0],";            } else {                $_setData .= "$_key=‘$_value‘,";            }        }        $_setData = substr($_setData, 0, -1);        $_sql = "UPDATE $_tables[0] SET $_setData $_where";        return $this->execute($_sql)->rowCount();    }        //验证一条数据    protected function isOne($_tables, Array $_param) {        $_where = ‘‘;        foreach ($_param as $_key=>$_value) {            $_where .=$_value.‘ AND ‘;        }        $_where = ‘WHERE ‘.substr($_where, 0, -4);        $_sql = "SELECT id FROM $_tables[0] $_where LIMIT 1";        return $this->execute($_sql)->rowCount();    }        //删除    protected function delete($_tables, Array $_param) {        $_where = ‘‘;        foreach ($_param as $_key=>$_value) {            $_where .= $_value.‘ AND ‘;        }        $_where = ‘WHERE ‘.substr($_where, 0, -4);        $_sql = "DELETE FROM $_tables[0] $_where LIMIT 1";        return $this->execute($_sql)->rowCount();    }        //查询    protected function select($_tables, Array $_fileld, Array $_param = array()) {        $_limit = $_order = $_where = $_like = ‘‘;        if (Validate::isArray($_param) && !Validate::isNullArray($_param)) {            $_limit = isset($_param[‘limit‘]) ? ‘LIMIT ‘.$_param[‘limit‘] : ‘‘;            $_order = isset($_param[‘order‘]) ? ‘ORDER BY ‘.$_param[‘order‘] : ‘‘;            if (isset($_param[‘where‘])) {                foreach ($_param[‘where‘] as $_key=>$_value) {                    $_where .= $_value.‘ AND ‘;                }                $_where = ‘WHERE ‘.substr($_where, 0, -4);            }            if (isset($_param[‘like‘])) {                foreach ($_param[‘like‘] as $_key=>$_value) {                    $_like = "WHERE $_key LIKE ‘%$_value%‘";                }            }        }        $_selectFields = implode(‘,‘, $_fileld);        $_table = isset($_tables[1]) ? $_tables[0].‘,‘.$_tables[1] : $_tables[0];        $_sql = "SELECT $_selectFields FROM $_table $_where $_like $_order $_limit";        $_stmt = $this->execute($_sql);        $_result = array();        while (!!$_objs = $_stmt->fetchObject()) {            $_result[] = $_objs;        }        return Tool::setHtmlString($_result);    }        //总记录    protected function total($_tables, Array $_param = array()) {        $_where = ‘‘;        if (isset($_param[‘where‘])) {            foreach ($_param[‘where‘] as $_key=>$_value) {                $_where .= $_value.‘ AND ‘;            }            $_where = ‘WHERE ‘.substr($_where, 0, -4);        }        $_sql = "SELECT COUNT(*) as count FROM $_tables[0] $_where";        $_stmt = $this->execute($_sql);        return $_stmt->fetchObject()->count;    }        //得到下一个ID    protected function nextId($_tables) {        $_sql = "SHOW TABLE STATUS LIKE ‘$_tables[0]‘";        $_stmt = $this->execute($_sql);        return $_stmt->fetchObject()->Auto_increment;    }    //执行SQL    private function execute($_sql) {        try {            $_stmt = $this->_pdo->prepare($_sql);            $_stmt->execute();        } catch (PDOException  $e) {            exit(‘SQL语句：‘.$_sql.‘<br />错误信息：‘.$e->getMessage());        }        return $_stmt;    }}?>