PDO 的 FETCH_INTO $这个类不起作用

2021-12-26 00:00:00 php pdo

我想使用 PDO 的 FETCH_INTO 的构造函数填充类:

I want to populate class with constructor using FETCH_INTO of PDO:

class user
{
    private $db;
    private $name;

    function __construct($id)
    {
        $this->db = ...;

        $q = $this->db->prepare("SELECT name FROM users WHERE id = ?");
        $q->setFetchMode(PDO::FETCH_INTO, $this);
        $q->execute(array($id));

        echo $this->name;
    }
}

这不起作用.没有错误，只是没有.脚本没有错误，FETCH_ASSOC 工作正常.

This does not work. No error, just nothing. Script has no errors, FETCH_ASSOC works fine.

FETCH_INTO 有什么问题?

推荐答案

您的代码中有两个错误:

You have two errors in your code:

1) 你忘记了 $q->fetch()

1) You forgot $q->fetch()

 ...
 $q->execute(array($id));
 $q->fetch(); // This line is required

2) 但即使在添加 $q->fetch() 之后你也会得到这个:

2) But even after adding $q->fetch() you'll get this:

致命错误:无法访问私有属性 User::$name in ...

Fatal error: Cannot access private property User::$name in ...

因此，如您所见，即使在类方法内部调用 PDO，它也无法访问私有成员.

So, as you can see, PDO cannot access private members even if it is called inside class method.

这是我的解决方案:

...
$q->execute(array($id));
$q->setFetchMode(PDO::FETCH_ASSOC);
$data = $q->fetch();
foreach ($data as $propName => $propValue)
{
    // here you can add check if class property exists if you don't want to
    // add another properties with public visibility
    $this->{$propName} = $propValue;
}

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