如何访问对象Twitter API中的对象？

I've started working with the Twitter API and Abraham's TwitterOAuth wrapper to retrieve Twitter data, but I can't figure out how to access objects within the array returned. The data is structured like so:

array(1) { [0]=> object(stdClass)#462 (24) { 
["created_at"]=> string(30) "Tue Sep 11 03:30:54 +0000 2018" 
["id"]=> int(120823024720) 
["id_str"]=> string(19) "1268383623782373" 
["text"]=> string(141) "RT @user: tweet tweet tweet tweet tweet" 
["truncated"]=> bool(false) 
["entities"]=> object(stdClass)#463 (4) { 
    ["hashtags"]=> array(0) { } 
    ["symbols"]=> array(0) { } 
    ["user_mentions"]=> array(1) { 
        [0]=> object(stdClass)#464 (5) { 
        ["screen_name"]=> string(6) "user" 
        ["name"]=> string(3) "username" 
        ["id"]=> int(12361328) 
        ["id_str"]=> string(8) "12342312" 
        ["indices"]=> array(2) { 
            [0]=> int(3) 
            [1]=> int(10) } } } 
        ["urls"]=> array(0) { } } 
        ["source"]=> string(82) "Twitter for iPhone" 
        ["in_reply_to_status_id"]=> NULL 
        ["in_reply_to_status_id_str"]=> NULL 
        ["in_reply_to_user_id"]=> NULL 
        ["in_reply_to_user_id_str"]=> NULL 
        ["in_reply_to_screen_name"]=> NULL 
        ["user"]=> object(stdClass)#465 (42)

There are many more layers, as tweets are actually extremely complex. I can access the first few pieces of data before the entities object, but, how do I access these sub-layers? Say, for instance, I want to access the screen name of the user. I have tried like so:

$data->entities->user_mentions->screen_name;

But I really have no idea to sort through this nested data. How do I navigate this data structure and access the different pieces of it?

First, the response is an array. So to get the first item from the array,

//get first item
$tweet = $data[0];

//user_mentions is also an array
$mention = $tweet->entities->user_mentions[0];

//now you can access the screen name with
$mention->screen_name;

If you wanted to iterate through an array of tweets,

foreach( $data as $tweet ) {
    $mention = $tweet->entities->user_mentions[0];
    echo $mention->screen_name;
}

Overall a fairly broad question. You should look into working with Arrays and Objects in PHP.