$query = $this->db->from(''user'')->where(array(''username'' => ''BobbyPeng''))->get();
return $query->row_array();

public function findByAttributes($where = array())
{
  $query = $this->db->from($this->tableName())->where($where)->get();
  return $query->row_array();
}

<&#63;php if ( ! defined(''BASEPATH'')) exit(''No direct script access allowed'');
class ActiveRecord extends CI_Model
{
  /**
   * 保存数据
   * 
   * @param array $data 需要插入的表数据
   * @return boolean 插入成功返回ID，插入失败返回false
   */
  public function save($data)
  {
    if($this->db->set($data)->insert($this->tableName())) {
      return $this->db->insert_id();
    }
    return FALSE;
  }
  /**
   * Replace数据
   * @param array $data
   */
  public function replace($data)
  {
    return $this->db->replace($this->tableName(), $data);
  }
  /**
   * 根据主键更新记录
   * 
   * @param string $pk 主键值
   * @param array $attributes 更新字段
   * @param array $where 附加where条件
   * @return boolean true更新成功 false更新失败
   */
  public function updateByPk($pk, $attributes, $where = array())
  {
    $where[$this->primaryKey()] = $pk;
    return $this->updateAll($attributes, $where);
  }
  /**
   * 更新表记录
   * 
   * @param array $attributes
   * @param array $where
   * @return bollean true更新成功 false更新失败
   */
  public function updateAll($attributes, $where = array())
  {
    return $this->db->where($where)->update($this->tableName(), $attributes);
  }
  /**
   * 根据主键删除数据
   * 
   * @param string $pk 主键值
   * @param array $where 附加删除条件
   * @return boolean true删除成功 false删除失败 
   */
  public function deleteByPk($pk, $where = array())
  {
    $where[$this->primaryKey()] = $pk;
    return $this->deleteAll($where);
  }
  /**
   * 删除记录
   * 
   * @param array $where 删除条件
   * @param int $limit 删除行数
   * @return boolean true删除成功 false删除失败
   */
  public function deleteAll($where = array(), $limit = NULL)
  {
    return $this->db->delete($this->tableName(), $where, $limit);
  }
  /**
   * 根据主键检索
   * 
   * @param string $pk
   * @param array $where 附加查询条件
   * @return array 返回一维数组，未找到记录则返回空数组
   */
  public function findByPk($pk, $where = array())
  {
    $where[$this->primaryKey()] = $pk;
    $query = $this->db->from($this->tableName())->where($where)->get();
    return $query->row_array();
  }
  /**
   * 根据属性获取一行记录
   * @param array $where
   * @return array 返回一维数组，未找到记录则返回空数组
   */
  public function findByAttributes($where = array())
  {
    $query = $this->db->from($this->tableName())->where($where)->limit(1)->get();
    return $query->row_array();
  }
  /**
   * 查询记录
   * 
   * @param array $where 查询条件，可使用模糊查询，如array(''name LIKE'' => "pp%") array(''stat >'' => ''1'')
   * @param int $limit 返回记录条数
   * @param int $offset 偏移量
   * @param string|array $sort 排序, 当为数组的时候 如：array(''id DESC'', ''report_date ASC'')可以通过第二个参数来控制是否escape
   * @return array 未找到记录返回空数组
   */
  public function findAll($where = array(), $limit = 0, $offset = 0, $sort = NULL)
  {
    $this->db->from($this->tableName())->where($where);
    if($sort !== NULL) {
      if(is_array($sort)){
        foreach($sort as $value){
          $this->db->order_by($value, '''', false);
        }
      } else {
        $this->db->order_by($sort);
      }
    }
    if($limit > 0) {
      $this->db->limit($limit, $offset);
    }
    $query = $this->db->get();
    return $query->result_array();
  }
  /**
   * 统计满足条件的总数
   * 
   * @param array $where 统计条件
   * @return int 返回记录条数
   */
  public function count($where = array())
  {
    return $this->db->from($this->tableName())->where($where)->count_all_results();
  }
  /**
   * 根据SQL查询， 参数通过$param绑定
   * @param string $sql 查询语句，如SELECT * FROM some_table WHERE id = &#63; AND status = &#63; AND author = &#63;
   * @param array $param array(3, ''live'', ''Rick'')
   * @return array 未找到记录返回空数组，找到记录返回二维数组
   */
  public function query($sql, $param = array())
  {
    $query = $this->db->query($sql, $param);
    return $query->result_array();
  }
}
/* End of file ActiveRecord.php */
/* Location: ./application/core/database/ActiveRecord.php */

<&#63;php if ( ! defined(''BASEPATH'')) exit(''No direct script access allowed'');
require_once APPPATH.''core/database/ActiveRecord.php'';
class MY_Model extends ActiveRecord 
{
  public function __construct($group_name = '''')
  {
    $this->initDb($group_name);
    parent::__construct();
  }
  protected function initDb($group_name = '''')
  {
    $db_conn_name = $this->getDbName($group_name);
    $CI = & get_instance();
    if(isset($CI->{$db_conn_name}) && is_object($CI->{$db_conn_name})) {
      $this->db = $CI->{$db_conn_name};
    } else {
      $CI->{$db_conn_name} = $this->db = $this->load->database($group_name, TRUE);
    }
  }
  private function getDbName($group_name = '''')
  {
    if($group_name == '''') {
      $db_conn_name = ''db'';
    } else {
      $db_conn_name = ''db_''.$group_name;
    }
    return $db_conn_name;
  }
}
/* End of file MY_Model.php */
/* Location: ./application/core/MY_Model.php */

CREATE TABLE `system_settings` (
 `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
 `key` varchar(64) NOT NULL DEFAULT '''',
 `value` mediumtext NOT NULL,
 `group` varchar(55) NOT NULL DEFAULT ''site'',
 `autoload` enum(''no'',''yes'') NOT NULL DEFAULT ''yes'',
 PRIMARY KEY (`id`,`key`),
 KEY `name` (`key`),
 KEY `autoload` (`autoload`)
) ENGINE=MyISAM AUTO_INCREMENT=11 DEFAULT CHARSET=utf8;

<&#63;php
if (!defined(''BASEPATH''))
  exit(''No direct script access allowed'');
class Setting {
  private $_ci;
  private $settings_autoloaded;
  private $settings = array();
  private $settings_group = array();
  private $settings_db;
  public function __construct() {
    $this->_ci = &get_instance();
    $this->settings_db = $this->_ci->config->item(''settings_table'');
    $this->autoload();
  }
  // ------------------------------------------------------------------------
  // 华丽的分割线 正式开始
  // ------------------------------------------------------------------------
  /**
   * 从数据库获取所有自动加载的设置
   */
  public function autoload() {
    //如果存在则直接返回
    if (!empty($this->settings)) {
      return $this->settings;
    }
    //如果系统不存在数据表则返回false
    if (!$this->_ci->db->table_exists($this->settings_db)) {
      return FALSE;
    }
    //查询标记为自动加载的项
    $this->_ci->db->select(''key,value'')->from($this->settings_db)->where(''autoload'', ''yes'');
    $query = $this->_ci->db->get();
    if ($query->num_rows() == 0) {
      return FALSE;
    }
    //循环写入系统配置
    foreach ($query->result() as $k => $row) {
      $this->settings[$row->key] = $row->value;
      $this->_ci->config->set_item($row->key, $row->value);
    }
    //标记会话，避免重复读库
    //$this->_ci->session->set_userdata(''settings_autoloaded'', TRUE);
    return $this->settings;
  }
  // ------------------------------------------------------------------------
  /**
   * 获取单个设定
   *
   * 
   * <&#63;php $this->settings->get(''config_item'');
   &#63;>
   * 
   */
  public function item($key) {
    if (!$key) {
      return FALSE;
    }
    //首先检查是否系统已经自动加载
    if (isset($this->settings[$key])) {
      return $this->settings[$key];
    }
    //查询数据库
    $this->_ci->db->select(''value'')->from($this->settings_db)->where(''key'', $key);
    $query = $this->_ci->db->get();
    if ($query->num_rows() > 0) {
      $row = $query->row();
      $this->settings[$key] = $row->value;
      return $row->value;
    }
    // 查询不到结果则查找系统config，返回值或者false
    return $this->_ci->config->item($key);
  }
  // ------------------------------------------------------------------------
  /**
   * 获取组配置
   */
  public function group($group = '''') {
    if (!$group) {
      return FALSE;
    }
    $this->_ci->db->select(''key,value'')->from($this->settings_db)->where(''group'', $group);
    $query = $this->_ci->db->get();
    if ($query->num_rows() == 0) {
      return FALSE;
    }
    foreach ($query->result() as $k => $row) {
      $this->settings[$row->key] = $row->value;
      $arr[$row->key] = $row->value;
    }
    return $arr;
  }
  // ------------------------------------------------------------------------
  /**
   * 更改设置
   */
  public function edit($key, $value) {
    $this->_ci->db->where(''key'', $key);
    $this->_ci->db->update($this->settings_db, array(''value'' => $value));
    if ($this->_ci->db->affected_rows() == 0) {
      return FALSE;
    }
    return TRUE;
  }
  // ------------------------------------------------------------------------
  /**
   * 新增设置
   */
  public function insert($key, $value = '''', $group = ''addon'', $autoload = ''no'') {
    // 检查是否已经被添加的设置
    $this->_ci->db->select(''value'')->from($this->settings_db)->where(''key'', $key);
    $query = $this->_ci->db->get();
    if ($query->num_rows() > 0) {
      return $this->edit($key, $value);
    }
    $data = array(''key'' => $key, ''value'' => $value, ''group'' => $group, ''autoload'' => $autoload, );
    $this->_ci->db->insert($this->settings_db, $data);
    if ($this->_ci->db->affected_rows() == 0) {
      return FALSE;
    }
    return TRUE;
  }
  // ------------------------------------------------------------------------
  /**
   * 删除设置
   */
  public function delete($key) {
    $this->_ci->db->delete($this->settings_db, array(''key'' => $key));
    if ($this->_ci->db->affected_rows() == 0) {
      return FALSE;
    }
    return TRUE;
  }
  // ------------------------------------------------------------------------
  /**
   * 删除设置组及成员配置
   */
  public function delete_group($group) {
    $this->_ci->db->delete($this->settings_db, array(''group'' => $group));
    if ($this->_ci->db->affected_rows() == 0) {
      return FALSE;
    }
    return TRUE;
  }
}
/* End of file Setting.php */
/* Location: ./application/libraries/Setting.php */

/**
 * 系统配置表名
 */
$config[''settings_table''] = "system_settings";

<&#63;php if ( ! defined(''BASEPATH'')) exit(''No direct script access allowed'');
class Hello extends CI_Controller {
  public function index()
  {
    echo "Hello CodeIgniter!";
  }
  public function showval($name){
    //访问路径：http://localhost/ci/index.php/hello/showval/Tom
    $this->name=$name;
    @$num=file_get_contents(''./num.txt'');//加上@屏蔽警告提示（第一次运行没有TXT文件会有警告提示）
    $num=$num&#63;$num:0;
    $num++;
    $arr=array(''v_name''=>$name,''v_num''=>$num);
    $re=fopen(''./num.txt'',''w'');
    fwrite($re,$num);
    fclose($re);
    $this->load->view(''test_views'',$arr);
  }
}

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>访问统计</title>
</head>
<body>
<&#63;php echo $v_name;&#63;>是第 <&#63;php echo $v_num;&#63;> 位访问者
</body>
</html>