CODE EXAMPLE FOR PHP

laravel parent child relationship in same table

namespace AppModels;

use IlluminateDatabaseEloquentFactoriesHasFactory;
use IlluminateDatabaseEloquentModel;

class Test extends Model
{
    use HasFactory;

    protected $parentColumn = 'parent_id';

    public function parent()
    {
        return $this->belongsTo(Test::class,$this->parentColumn);
    }

    public function children()
    {
        return $this->hasMany(Test::class, $this->parentColumn);
    }

    public function allChildren()
    {
        return $this->children()->with('allChildren');
    }

}