How to correctly add record to related tables laravel?

Question

Laravel

I looked at the manuals, but it’s a bit different from what I need
. I have 2 entities (post and categories) one-to-many relationship
in the code, there may be errors because I write about the method
in the request, an array with category id comes

$post = new Post();
$post->fill($request->validate());
$post->save();

foreach($request->query('categories') as $cat){
 $categories = Categories::find($cat);
$categoris->post_id = $post->id;
$categoies->save();
}

It seems to me that this method is kind of tricky, can you tell me if there is another option to update, (the post and category entities are taken as an example)

Answer 1

$post->categories()->sync($request->get('categories'));

Answer 2

Documentation

$post = new Post();
$post->create($request->all());

foreach($request->get('categories') as $categoryId){
 $category = Categories::find($categoryId);
 $post->categories()->save($category);
}