laravel parent child in same table

gistfile1.txt

class ProjectTree extends Model {
  //each category might have one parent
    public function parent() {
        return $this->belongsToOne(static::class, 'parent_id');
    }
    //each category might have multiple children
    public function children() {
        return $this->hasMany(static::class, 'parent_id')->orderBy('name', 'asc');
    }
}

$ProjectTree = ProjectTree::where('id',$id)->with([
                    'children'=>function($query){
                        $query->with([
                            'children'=>function($query){
                                $query->with(['children'=> function($query){
                                    $query->with('children');
                                }]);
                            }]);
       }])->select(['id'])->get();

<ul>
  @foreach ($categories as $parent)
    <li>{{ $parent->cat_name }}
      @if ($parent->children->count())
        <ul>
          @foreach ($parent->children as $child)
            <li>{{ $child->cat_name }}</li>
          @endforeach
        </ul>
      @endif
    </li>
  @endforeach
</ul>