Eloquent mass assignment from multi-dimentional array along with model relationships

I've got a multidimensional array coming from $_POST. Its keys are exactly the same as either columns in the blog_posts table or names of its relations (e.g. author).

I would like to mass assign the $_POST to a matching object and its relations. Example:

$_POST = array (
    'blog_post' => array (
        'title' => 'the title of the post',
        'content' => 'the content of the post',
        'date' => '23-09-2015',
        'author' => array (
            'name' => 'hydra',
            'age' => 47,
            'location' => 'Russia',
        ),
    ),
);

would be mapped to a blog_post object and a author object.

2 things to keep in mind:

• this is only an example, i've no clue what type of objects i'll be working with;
• the solution should also be usable with collections of objects

my current (obviously non-working) solution would involve:

array_walk($_POST, function(value, key){
    if (is_array($value) && class_exists($key)) {
        $object = new $key($value);
        $object->save();
    }
});

This only saves the first object (blog_post).

via Chebli Mohamed