many_to_many.php

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Article extends Model
{

  protected $fillable = ['name', 'content'];

  public function laws()
  {
    return $this->belongsTo(Law::class);
  }

  public function articles() 
  {
    return $this->belongsToMany(Article::class);
  }

}