<?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;

    }

}

?>