Why json_encode() return keys values twice (index key and string key)?

Question

When I use the json_encode() function, the method return a Json with two time the same value: one with the string key and one with an index. I did not have this problem before.

$req = $bdd->prepare("SELECT mail,description FROM identifiant WHERE mail = :mail AND pass=:pass");
        if ($req->execute(array(
                    'mail' => $_COOKIE['mail'],
                    'pass' => $_COOKIE['pass']))) {
            header('Content-type: application/json');

            return json_encode($req->fetchAll());

The response:

[
   {
      "mail": "[email protected]",
      "0": "[email protected]",
      "description": "a description",
      "1": "a description"
   }
]

How can I do for don't have index keys ?

Answer 1

Use PDO::FETCH_ASSOC fetching mode:

return json_encode($req->fetchAll(PDO::FETCH_ASSOC));

Answer 2

It's not json_encode, it's because your PDO instance's fetch mode is set to PDO::FETCH_BOTH. See the documentation for PDOStatement::fetchAll's fetch style.