Returning a blob with json

Question

I'm trying to create a rest service for my android application where an external database returns items to be stored in the applications local database. I've got everything working except blobs are being returned as null.

this is an example of my jason response.(picture and thumbnail fields are blobs)

{"id":"2","user_id":"1","name":"testing","type":"bouldering","picture":null,"lat":"36","long":"81","alt":"41932","accuracy":"53","thumbnail":null}

Here is my php script to return the data.

<?php
require_once('config.php');

$mysqli = new mysqli(DB_HOST,DB_USER,DB_PASSWORD,DB_NAME);
$sql = 'select * from spot_main';
$results =$mysqli->query($sql);

$spots = array();  //array to parse jason from

while($spot = $results->fetch_assoc()){
    $spots[] = $spot;                                                           
}

echo json_encode($spots);
?>

Anyone know of a solution to this problem? I know I'm not doing this the most efficient way(better to store images in the filesystem), but I need this to work.

Answer 1

Encode the binary data as base64 before you generate the JSON.

$obj->picture = base64_encode($binaryData);

You can then decode this in your Android application with any base 64 decoder. Since API level 8 there is a built in util class. Otherwise there are plenty of external libs you can use for targetting Android 2.1 or earlier.

Answer 2

you have to make BLOB to base64_encode

 while($spot = $results->fetch_assoc()){
     $spots[] = $spot;                                                           
    }

Then prepare a foreach loop like this

foreach($spots as $key=>$value){
    $newArrData[$key] =  $spots[$key];
    $newArrData[$key]['picture'] = base64_encode($spots[$key]['picture']);
    $newArrData[$key]['thumbnail'] = base64_encode($spots[$key]['thumbnail']);
}
header('Content-type: application/json');
echo json_encode($newArrData);

Answer 3

It seems that json_encode works with UTF-8 encoded data only. You can use json_last_error() to detect json_encode error.