来自数据库的BLOB /二进制列的输出值

Question

i've a field in a database which is saved as binary data. I just want to put out the data, that is in that field.

I used the following code but get no output. What's going wrong?

 $pdo = new PDO('sqldata);


$sql = 'SELECT name, datei FROM download WHERE id = 9';
$blob = 'SELECT CONVERT(datei USING utf8) FROM download WHERE id = 9';

    foreach ($pdo->query($sql) as $row) { //for testing that the db-query works
        echo $row['name'] . $row['datei'].'<br>';
    } 

    foreach ($pdo->query($blob) as $row1) {
        echo $row1['datei'].'<br>';
    }