How to Build Nested Tree Structures for Parent-Child using The Laravel Eloquent Relationships

A few days back, working on a Laravel project I had to create an API returning the deeply nested Tree structure for the parent-child relationship of a given object entity - in this case, a Company.

Although as an experienced PHP developer, I know how to build Nested Tree Structures for Parent-Child relationships using core PHP and SQL queries. But I was looking to, if Laravel Eloquent provides any efficient inbuilt method to fetch the Parent-child relationship with a deep nested tree structure.

This led me to search on ChatGPT for the same. Here I want to give credit to ChatGPT which not only saved my time but also suggested a new way to get the desired result using Laravel Eloquent Relationships.

Before I explain the solution for building a Nested Tree Structure, first let's understand it.

Understanding Nested Tree Structures:

A nested tree structure organizes data in a hierarchical manner, making it easy to represent parent-child relationships. Each node in the tree can have multiple children, creating a flexible and intuitive structure.

Setting up the Database:
Start by setting up a table in your database to store the companies. Include a parent_company column to establish the parent-child relationship. This column will contain the ID of the parent company.

Defining the Model:
Create a model for your company table using Laravel Eloquent. This model will enable you to interact with the database and perform operations on the data. 

class Company extends Model
{
    protected $fillable = ['name', 'parent_company'];
}

Building the Tree Structure:
To construct a nested tree structure, utilize methods provided by Laravel Eloquent. For instance, you can use the `hasMany` relationship to define the children of a company:

class Company extends Model
{
    public function children()
    {
        return $this->hasMany(Company::class, 'parent_company', 'id');
    }

    public function descendants(): HasMany
    {
        return $this->children()->with('descendants')->withCount('users');
    }
}

Retrieving the Tree with Children:
Now, fetching the entire nested tree becomes straightforward. Suppose you want to retrieve all companies with their respective children:

$companies = Company::with('children')->get();

Retrieving the Tree with Descendants:
Fetching the entire nested tree along with descendants becomes a simple eloquent query:

$companies = Company::with('descendants')->get();

So this is how using Laravel Eloquent, I have easily built and managed nested tree structures for parent-child relationships. This approach enhances the readability and maintainability of your code, providing a solid foundation for handling hierarchical data.

I hope this will help you learn the basics of creating a nested tree structure in Laravel Eloquent. Feel free to explore additional features and customization options to suit your specific needs.