Laravel，如何在使用belongsToMany时过滤行？

I'm confused about the Laravel API and its many to many relationship model.

There are the following tables:

posts tags post_tag

And I want to find posts which have tagId = 123

Is there simple source code similar to the following?

$posts= Post::find()->pivot->tag(123);

Thanks.

You should specify the method in Tag model:

public function posts()
{
    return $this->belongsToMany('App\Post');
}

Then you can find posts which have tagId = 123

$posts = Tag::find(123)->posts();