Array 1 holds keys which are allowed in Array 2.

index.php

foreach($articles->category->devices as $device) { // Iterate through all objects
	foreach ($device as $key => $value) { // Iterate through all properties
		if (!in_array($key, $allowedFields)) { // Find property in pre-defined array with the properties which are allowed for this object
			unset($device->$key); // unset the properties which doesn't match the array
		}
	}
}