PHP - Access Object Attributes Dynamically

I want to access object attributes with child objects dynamically just by specifying the attribute in a string variable. 

$book->category->name

$attr="category->name";

$book=\App\Models\Book::find(2);

echo $book->$attr;

Result : null

Solution :

$attr="category->name";

$book=\App\Models\Book::find(2);

$parts=explode("->",$attr);

$h=$book;

foreach($parts as $p){

    $h=$h->$p;

}

echo $h;

Result : book category name