php - 从扩展类调用其对象时出现 PDO rowCount() 错误

Question

我创建了一个数据库类，它使用 PDO 连接到我的查询，我在主类构造函数中将其作为对象调用。

class MyClass
{
    protected $db;

    public __constructor()
    {
        $this->db = new Database();
    }
}
class Themes extends MyClass
{
    public $avatar;
    public $theme_name;
    public $theme_by;
    public $theme_by_email;
    public $theme_by_website;
    public $theme_description;
    public $theme_thumb;
    public $theme_source;
    public $theme_css;
    public $theme_js;
    public $theme_uploaded_on;

    public function __construct()
    {
        parent::__construct();
        $this->get_theme();
        $this->get_avatar();
    }

    public function get_theme()
    {
        $sql = "SELECT *
                FROM `user_themes`
                WHERE `user_id` = " . $this->session->get('user_id');
        if($this->db->row_count($sql))
        {
            $result                  = $this->db->fetch_row_assoc($sql);
            $this->theme_name        = $result['theme_name'];
            $this->theme_by          = $result['theme_by'];
            $this->theme_by_email    = $result['theme_by_email'];
            $this->theme_by_website  = $result['theme_by_website'];
            $this->theme_description = $result['theme_description'];
            $this->theme_source      = $result['theme_source'];
            $this->theme_css         = $result['theme_css'];
            $this->theme_js          = $result['theme_js'];
            $this->theme_uploaded_on = $result['theme_uploaded_on'];
        }else{
            die('no results');
        }
    }
}

我的问题是，如果我包含调用 MyClass 构造函数的扩展类，则会出现此错误:

Fatal error: Call to a member function rowCount() on a non-object in db.class.php on line 98

它指向我的 db.class.php 中的这一行

class Database {

    private static $PDO;
    private static $config;

    public function __construct() {

        if (!extension_loaded('pdo'))
            die('The PDO extension is required.');

        self::$config = config_load('database');

        self::connect();

    }
...
    public function row_count($statement)
    {
        return self::$PDO->query($statement)->rowCount(); //Line 98
    }
}

如果我从我的扩展类中注释掉 parent::__construct() 那么我就没问题并且没有错误。

在 FireFox、Chrom、Opera 和 Safari 中试用我的网站

http://www.helixagent.com

我在 Firefox 3.6 中似乎没问题，但所有其他浏览器都会向我抛出我提到的错误...

Answer 1

将您的 row_count-method 更改为此:

public function row_count($statement)
{
  self::$PDO->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
  try {
    $stmt = self::$PDO->query($statement); 
    $result = $stmt->rowCount();
    return $result;
  } catch (PDOException $e) { echo $e->getMessage(); }

    return false;
}

现在你至少知道出了什么问题。