$json1 = '{"data": [{"category": "Games","id": "45345"}, {"category": "Music","id": "345345345"}, {"category": "Food","id": "1"}, {"category": "Pets","id": "13245345"}],"paging": {"next": "https://graph.facebook.com/1161990140/likes?limit=2&offset=2&__after_id=118243704898877"}}';
    $json2 = '{"data":  {"something": "blah","posts":  [{"id": "34241","title": "orange"}],"items":  [{"id": "1","name": "orange"},{"id": "2","name": "dog"},{"id": "3","name": "cat"},{"id": "4","name": "apple"}]}}';

    $array1 = json_decode($json1, true);
    $array2 = json_decode($json2, true);

    $result = array_diff($array1, $array2);

    var_dump($result);