Question

使用PDO::setAttribute，如何在PDO::ATTR_DEFAULT_FETCH_MODE设置为PDO::FETCH_CLASS时提供类名。

这是我正在使用的代码..我想设置它以便将所有行作为DB_Row的实例返回：

class DB_Row extends ArrayObject {}

$db = new PDO('mysql:dbname=example;host=localhost', 'user', 'pass');
$db->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_CLASS);

$stmt = $db->query("SELECT * FROM `table` WHERE `id` = 1;");

$row = $stmt->fetch(); // I want a DB_Row by default!

上面的代码导致PDOException，因为未分配DB_Row类名。

Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000]: General    error: No fetch class specified

我该怎么做？

提前致谢..

解决方案：我使用了 fireeyedboy 的回答。它对我的情况起了最好的作用，因为我已经将PDOStatement用于记录目的......

class DB extends PDO {
    public function __construct($host = null, $user = null, $pass = null, $db = null) {
        try {
            parent::__construct('mysql:dbname=' . $name .';host=' . $host, $user, $pass);
            $this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            $this->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_CLASS);
            $this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('DB_Query', array('DB_Row')));
        } catch (PDOException $e) {
            die('Database Error');
        }
    }
}

class DB_Query extends PDOStatement {
    private $class;
    protected function __construct ($class = 'DB_Row') {
        $this->class = $class;
        $this->setFetchMode(PDO::FETCH_CLASS, $this->class);
    }
}

class DB_Row extends ArrayObject {
    public function __set($name, $val) {
        $this[$name] = $val;
    }
    public function __get($name) {
        return $this[$name];
    }
}

Answer 1

我认为它应该返回一个stdclass实例，所以这将是一个错误 - 但是必须在代码中查找它以进行验证。如果在那之前没有接受的答案，我们会这样做。

使用PDO :: FETCH_CLASS |将起作用PDO :: FETCH_CLASSTYPE然后提供类名作为第一列。虽然这是一个黑客：

$db->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_CLASS | PDO::FETCH_CLASSTYPE);

$stmt = $db->query("SELECT 'classname', * FROM `table` WHERE `id` = 1;");

编辑：正如这里承诺的那样。相关代码在这里http://lxr.php.net/xref/PHP_5_4/ext/pdo/pdo_stmt.c#940因此，只有使用FETCH_CLASSTYPE才能设置for fetch（）。另一种方法是使用PDOStatement :: fetchObject（）

Answer 2

另一种黑客方法是扩展PDOStatement，覆盖其获取方法，让你的PDO实例将其用作默认语句类。

作为一个例子，我只是展示覆盖fetch() ¹并离开fetchAll()，如果你想走这条路，那么你有什么打算：

class Db_Row
{
}

class PDOStatementWithClass
    extends PDOStatement
{
    private $fetch_class;

    // PHP complained when I tried to make this public
    protected function __construct( $fetch_class = 'StdClass' )
    {
        // internally set the fetch class for later use
        $this->fetch_class = $fetch_class;
    }

    // let $fetch_style default to PDO::FETCH_CLASS in stead of PDO::FETCH_BOTH
    public function fetch( $fetch_style = PDO::FETCH_CLASS, $cursor_orientation = PDO::FETCH_ORI_NEXT, $cursor_offset = 0 )
    {
        // make sure we're really dealing with the correct fetch style
        if( $fetch_style == PDO::FETCH_CLASS )
        {
            // then automatically set the fetch mode of this statement
            parent::setFetchMode( $fetch_style, $this->fetch_class );
        }

        // go ahead and fetch, we should be good now
        return parent::fetch( $fetch_style, $cursor_orientation, $cursor_offset );
    }
}

$db = new PDO( /* etc... */ );
// set default fetch mode to FETCH_CLASS
$db->setAttribute( PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_CLASS );
// override what statement class to use, and provide constructor arguments (found out by trial and error)
$db->setAttribute( PDO::ATTR_STATEMENT_CLASS, array( 'PDOStatementWithClass', array( 'Db_Row' ) ) );

这样做的另一个好处是，您只需在应用程序中定义PDO::FETCH_CLASS一次，而不是在每个查询中定义。{/ p>

<小时/> ^{1）我很惊讶PHP并没有抱怨在方法中覆盖方法的签名。}

Answer 3

public function fetchAll($fetch_style = \PDO::FETCH_CLASS, $fetch_argument = null, $ctor_args = null) {
    if ($fetch_style == \PDO::FETCH_CLASS){
        parent::setFetchMode( $fetch_style, 'App\Core\DBFetch' );
    }
    $fetchedData = call_user_func_array(array('parent', __FUNCTION__), func_get_args());
    return $fetchedData;
}

在PHP中，如何设置默认的PDO Fetch Class？

3 个答案: