成员函数行

我尝试在脚本中运行查询并收到此消息。有人知道为什么和如何解决它吗?

致命错误:在非对象上调用成员函数row()

$query_str = "SELECT MAX(userID) FROM kowmanager_users";
$this->db->query($query_str);
$row = $query->row(); 
$userID = $row->userID;

编辑:

我找到了这里的语法:http://codeigniter.com/user_guide/database/active_record.html#select

并提出了这个为我的需要，但当我运行脚本它给了我一个你有一个错误在你的SQL语法;查看与MySQL服务器版本对应的手册，以便在第1行

处的'Object'附近使用正确的语法。

文件名:/home/xtremer/public_html/kowmanager/模型/user_model.php

$this->db->select_max('userID');
$query_str = $this->db->get('kowmanager_users');
$rows = $this->db->query($query_str);
$userID = $rows->userID;
$userID = $userID + 1;

编辑2:

由于某些原因，更新没有运行。

 $query_str = "INSERT INTO kowmanager_users (username, password, password2, email, firstName, lastName, accessLevelID) VALUES (?, ?, ?, ?, ?, ?, ?)";
    $this->db->query($query_str, array($username, $password[0], $password[1], $email, $firstName, $lastName, '1',));
    $id = $this->db->insert_id();
    $this->db->select_max('userID');
    $query = $this->db->get('kowmanager_users');
    $row = $query->row();
    $userID = $row->userID;
    echo $userID;
    echo "<br>";
    $userID = $userID + 1;
    echo $userID;
    $data = array('userID' => $userID);
    $where = "id = '".$id."'"; 
    $str = $this->db->update_string('kowmanager_users', $data, $where); 

编辑:这是我的完整页面代码:http://pastebin.com/7sJt7V09

$query_str = "SELECT MAX(userID) FROM kowmanager_users";
$q = $this->db->query($query_str);
$row = $q->row(); 
$userID = $row->userID;

$this->db->select_max('userID');
$q = $this->db->get('kowmanager_users');
$row = $q->row();
$userID = $row->userID;

$this->db->select('userID');
$q = $this->db->get('kowmanager_users');
$results = $q->result();
foreach($results as $row) 
{
 echo $row->userID; 
}

$row = $this->db->query->row();