How to add a new element to every item of collection? Laravel

from

To

 $posts->map(function ($post) {
    $post['url'] = 'http://your.url/here';
    return $post;
});

or (if its Error "Cannot use object of type stdClass as array")

$posts->map(function ($post) {
    $post->url = 'http://your.url/here';
    return $post;
});

source : https://laracasts.com/discuss/channels/laravel/how-to-add-a-new-element-to-every-item-of-collection