I’m working on a project using Laravel v9.19 and PHP 8.0.

Here is a part of that project’s database which is relevant to the question:

• One user can have many orders, but each order has only one user (one-to-many relationship).
• One order can have only one item, but one item may be present in many orders (many-to-one relationship).

Here is a User class:

class User extends Authenticatable
{
    // ...

    /**
     * Get orders of this user.
     * 
     * @return IlluminateDatabaseEloquentRelationsHasMany
     */
    public function orders(): HasMany
    {
        return $this->hasMany(Order::class, 'client_id');
    }
}

Here is an Order class:

class Order extends Model
{
    // ...

    /**
     * Get the client of this order.
     * 
     * @return IlluminateDatabaseEloquentRelationsBelongsTo
     */
    public function client(): BelongsTo
    {
        return $this->belongsTo(User::class, 'client_id');
    }

    /**
     * Get the ordered item.
     * 
     * @return IlluminateDatabaseEloquentRelationsBelongsTo
     */
    public function item(): BelongsTo
    {
        return $this->belongsTo(Item::class, 'item_id');
    }
}

Here is an Item class:

class Downloadable extends Model
{
    // ...

    /**
     * Get the orders having this item.
     * 
     * @return IlluminateDatabaseEloquentRelationsHasMany
     */
    public function orders(): HasMany
    {
        return $this->hasMany(Order::class, 'item_id');
    }
}

I would like to utilize the Eloquent Relationships in order to make it possible to:

• Retrieve all items ordered by a specific user.
• Retrieve all users that ordered a specific item.

I will need to add a new method to the User model:

    /**
     * Get items ordered by this user.
     * 
     * @return ???
     */
    public function items()
    {
        // What to do here?
    }

I will need to add a new method to the Item model:

    /**
     * Get users that ordered this item.
     * 
     * @return ???
     */
    public function users()
    {
        // What to do here?
    }

Since the default HasManyThrough relationship requires a different table structure, and I cannot modify the existing table structure, it’s not applicable here.

As one of possible solutions I’m considering to use staudenmeir/eloquent-has-many-deep, creating a new intermediate table named order_item to map orders to items, and use the following code, for example, for the items method:

    /**
     * Get items ordered by this user.
     * 
     * @return ???
     */
    public function items()
    {
        return $this->hasManyDeep(
                    Item::class,
                    [Order::class, 'order_item']
            );
    }

If there exists a Laravel solution without external libraries, or you know something more efficient, please share that to me. I’m eager to know the best practice for that case.