Laravel - Count self referencing relations

Sorry for responding to an old question, but i were looking to solve this issue myself and i came up with this solution which seems to work out quite well perhaps you can use it to solve your issue with this.

By eager loading the children we avoid multiple queries during the count loop, downside of always eager loading the children is if it's long and deep relationships which might return a lot of data so test it out if it performs well enough for your use case.

Some performance gains can be made by using correct indexing on your database and making sure your database is well structured, this shouldn't by any means be slow since it's a single query/done in the same query as fetching a single row.

Avoid eager loading both parent and children since they're self-referencing and will cause an infinite loop

By adding the eager load we can then loop through the relationships and return a total count of children, see the code below.

class User extends Model{
   protected $append = ['children_count'];
   protected $with = ['children']; //Eager load the relationship

   public function parent()
   {
    return $this->belongsTo(User::class, 'parent_id', 'id');
   }

   public function children()
   {
    return $this->hasMany(User::class, 'parent_id', 'id');
   } 

   public function getChildrenCountAttribute()
   {
       $count = $this->children->count(); //This specific models count

       //Loop through the already loaded children and get their count
       foreach($this->children as $child){
          $count += $child->children->count(); //Sum up the count
       }

       return $count; //Return the result
   }
}

what if you append a new attribute to the model

class User extends Model{
   protected $append = ['children_count'];

   public function getChildrenCountAttribute()
   {
       return $this->children()->count();
   }
}

Now you get number of a user's children without getting children

$user->children_count;