PDO result array cannot be turned into json

Question

I've seen many examples on the internet (especially here) where the solution below should be able to turn the result of a database query into JSON:

    $stmt = $pdo->query('select * from TABLE;');
    $data = $stmt->fetchAll(PDO::FETCH_ASSOC);
    echo json_encode($data);

but in my case this doesn't produce any JSON, although the query result contains 75 rows. A slightly different approach does return JSON:

    $stmt = $pdo->query('select * from TABLE;');
    echo "[";
    while($r = $stmt->fetch()) {
        echo json_encode($r);
    }
    echo "]";

I could go with that, but I am wondering what is going on. Why is the first approach not working?

EDIT:

this might give a clue. The code below produces [] as a result. Still not what I want, but the fetch in the while statement does 'something' .

    $stmt = $pdo->query('select * from TABLE;');
    while($r = $stmt->fetch()) {}
    $data = $stmt->fetchAll(PDO::FETCH_ASSOC);
    echo json_encode($data);

Do you realize that it simple can't be? If second query returns something, then firs will return a well. — Your Common Sense, Apr 09 '14 at 19:55
Make sure your data is encoded correctly http://stackoverflow.com/questions/19361282/why-would-json-encode-returns-an-empty-string — tlenss, Apr 09 '14 at 19:56
@YourCommonSense because he is using `->fetchAll(PDO::FETCH_ASSOC)` — tlenss, Apr 09 '14 at 19:58
@tlenss what? "because"? May be you can explain, how this code can make any sense when used with ->fetchAll? — Your Common Sense, Apr 09 '14 at 19:59

Your Common Sense · Answer 1 · 2014-04-09T19:55:05.510

2

Why is the first approach not working?

It does. Just double check the resulting JSON.
As long as your query returns any rows, this code produces perfect, first class json.

Most likely, like other PHP users, you are checking not the immediate result but distant consequences.

If it really doesn't, then check json_last_error() and then set your database client encoding in utf8

edited Apr 09 '14 at 19:55

answered Apr 09 '14 at 19:47

Your Common Sense

156,878
40
214
345

What do you mean that I am checking distant consequences? – Walter Brand Apr 09 '14 at 19:50
I mean you are checking anything but json returned by this code. May be some image in the browser or something like that. – Your Common Sense Apr 09 '14 at 19:51
json_last_error() returns 5 which apparently means that I have a problem with the utf8 encoding.I will look into it. Thanks for showing me the right direction! – Walter Brand Apr 09 '14 at 20:03
@WalterBrand if first code returns nothing, then second should return the same. – Your Common Sense Apr 09 '14 at 20:05
somehow the second one produces json. – Walter Brand Apr 09 '14 at 20:07

PDO result array cannot be turned into json

1 Answers1