send json object from javascript to php

The standard jQuery .ajax() method uses the data property to create an x-www-form-urlencoded string to pass in the request body. Something like this

action=Flickr&get=getPublicPhotos

Therefore, your PHP script should not look for $_POST['data'] but instead, $_POST['action'] and $_POST['get'].

If you want to send a raw JSON data payload to PHP, then do the following…

Set the AJAX contentType parameter to application/json and send a stringified version of your JSON object as the data payload, eg

$.ajax({
    url: '../phpincl/apiConnect.php',
    type: 'POST',
    contentType: 'application/json',
    data: JSON.stringify(flickrObj),
    dataType: 'json'
})

Your PHP script would then read the data payload from the php://input stream, eg

$json = file_get_contents('php://input');

You can then parse this into a PHP object or array…

$dataObject = json_decode($json);
$dataArray = json_decode($json, true);

And, if you’re just wanting to echo it back to the client..

header('Content-type: application/json');

// unmodified
echo $json;

// or if you've made changes to say $dataArray
echo json_encode($dataArray);