class dbconfig {
    private static $dbms = "mysql";
    private static $host = '127.0.0.1';
    private static $port = '3306';
    private static $username = '';
    private static $password = '';
    private static $dbname = '';
    private static $charset = 'utf-8';
    private static $dsn;
 
    /**
     *
     * @return   返回pdo dsn配置
     */
    public static function getdsn() {
        if (!isset(self::$dsn)) {
            self::$dsn = self::$dbms . ':host=' . self::$host . ';port=' .
                    self::$port . ';dbname=' . self::$dbname;
            if (strlen(self::$charset) > 0) {
                self::$dsn = self::$dsn . ';charset=' . self::$charset;
            }
        }
        return self::$dsn;
    }
 
    /**
     * 设置mysql数据库服务器主机
     * @param  $host 主机的ip地址
     */
    public static function sethost($host) {
        if (isset($host) && strlen($host) > 0)
            self::$host = trim($host);
    }
 
    /**
     * 设置mysql数据库服务器的端口
     * @param  $port 端口
     */
    public static function setport($port) {
        if (isset($port) && strlen($port) > 0)
            self::$port = trim($port);
    }
 
    /**
     * 设置mysql数据库服务器的登陆用户名
     * @param  $username
     */
    public static function setusername($username) {
        if (isset($username) && strlen($username) > 0)
            self::$username = $username;
    }
 
    /**
     * 设置mysql数据库服务器的登陆密码
     * @param  $password
     */
    public static function setpassword($password) {
        if (isset($password) && strlen($password) > 0)
            self::$password = $password;
    }
 
    /**
     * 设置mysql数据库服务器的数据库实例名
     * @param  $dbname 数据库实例名
     */
    public static function setdbname($dbname) {
        if (isset($dbname) && strlen($dbname) > 0)
            self::$dbname = $dbname;
    }
 
    /**
     * 设置数据库编码
     * @param  $charset
     */
    public static function setcharset($charset) {
        if (isset($charset) && strlen($charset) > 0)
            self::$charset = $charset;
    }
 
}
 
/**
 * 一个数据库操作工具类
 *
 * @author zhjiun@gmail.com 
 */
class dbtemplate {
 
    /**
     * 返回多行记录
     * @param  $sql
     * @param  $parameters
     * @return  记录数据
     */
    public function queryrows($sql, $parameters = null) {
        return $this->exequery($sql, $parameters);
    }
 
    /**
     * 返回为单条记录
     * @param  $sql
     * @param  $parameters
     * @return
     */
    public function queryrow($sql, $parameters = null) {
        $rs = $this->exequery($sql, $parameters);
        if (count($rs) > 0) {
            return $rs[0];
        } else {
            return null;
        }
    }
 
    /**
     * 查询单字段，返回整数
     * @param  $sql
     * @param  $parameters
     * @return
     */
    public function queryforint($sql, $parameters = null) {
        $rs = $this->exequery($sql, $parameters);
        if (count($rs) > 0) {
            return intval($rs[0][0]);
        } else {
            return null;
        }
    }
 
    /**
     * 查询单字段，返回浮点数(float)
     * @param  $sql
     * @param  $parameters
     * @return
     */
    public function queryforfloat($sql, $parameters = null) {
        $rs = $this->exequery($sql, $parameters);
        if (count($rs) > 0) {
            return floatval($rs[0][0]);
        } else {
            return null;
        }
    }
 
    /**
     * 查询单字段，返回浮点数(double)
     * @param  $sql
     * @param  $parameters
     * @return
     */
    public function queryfordouble($sql, $parameters = null) {
        $rs = $this->exequery($sql, $parameters);
        if (count($rs) > 0) {
            return doubleval($rs[0][0]);
        } else {
            return null;
        }
    }
 
    /**
     * 查询单字段，返回对象，实际类型有数据库决定
     * @param  $sql
     * @param  $parameters
     * @return
     */
    public function queryforobject($sql, $parameters = null) {
        $rs = $this->exequery($sql, $parameters);
        if (count($rs) > 0) {
            return $rs[0][0];
        } else {
            return null;
        }
    }
 
    /**
     * 执行一条更新语句.insert / upadate / delete
     * @param  $sql
     * @param  $parameters
     * @return  影响行数
     */
    public function update($sql, $parameters = null) {
        return $this->exeupdate($sql, $parameters);
    }
 
    private function getconnection() {
        $conn = new pdo(dbconfig::getdsn(), dbconfig::getusername(), dbconfig::getpassword());
        $conn->setattribute(pdo::attr_case, pdo::case_upper);
        return $conn;
    }
 
    private function exequery($sql, $parameters = null) {
        $conn = $this->getconnection();
        $stmt = $conn->prepare($sql);
        $stmt->execute($parameters);
        $rs = $stmt->fetchall();
        $stmt = null;
        $conn = null;
        return $rs;
    }
 
    private function exeupdate($sql, $parameters = null) {
        $conn = $this->getconnection();
        $stmt = $conn->prepare($sql);
        $stmt->execute($parameters);
        $affectedrows = $stmt->rowcount();
        $stmt = null;
        $conn = null;
        return $affectedrows;
    }
}