Category Tree from multilevel categories in one Query in Laravel 9

To generate a category tree from a multilevel category structure in one query using Laravel 9, you can use a recursive function and a self-join. Here’s an example:

First, create a categories table in your database with the following columns: id, name, and parent_id.

Next, create a model for the Category table:

php artisan make:model Category

Then, add the following function to the Category model:

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

This function defines a one-to-many relationship between categories, where each category can have many children.

Now, in your controller, you can use the following code to retrieve the category tree:

$categories = Category::with('children')->where('parent_id', null)->get();

function buildTree($categories)
{
    $tree = [];

    foreach ($categories as $category) {
        $children = $category->children;

        if ($children->isNotEmpty()) {
            $category->children = buildTree($children);
        }

        $tree[] = $category;
    }

    return $tree;
}

$categoryTree = buildTree($categories);

The with('children') method eager loads the children for each category, and the where('parent_id', null) condition filters out the top-level categories.

The buildTree function recursively builds the category tree by iterating through each category’s children and calling itself with the children as the argument. The function also replaces the children attribute of each category with its own children, so that the resulting array contains the full category tree.

Finally, you can return the category tree to your view and display it as needed.

Use case of Category Tree

The use case for generating a category tree from a multilevel category structure in one query using Laravel 9 is common in many web applications. A category tree is a hierarchical structure that organizes data into a logical and intuitive order. It is used to group and organize products, articles, and other types of content, making it easier for users to navigate and find what they’re looking for.

One example of a use case for generating a category tree is in an e-commerce website. An e-commerce website may have thousands of products organized into categories and subcategories. The category tree can help users quickly locate the products they are interested in by displaying the categories and subcategories in a structured format. Users can then click on a category or subcategory to view the products within that category.

Another use case for generating a category tree is in a content management system (CMS) or blog platform. In a CMS or blog platform, articles and other content are typically organized into categories and subcategories. The category tree can help users easily navigate through the articles and find content that is relevant to them. Users can click on a category or subcategory to view all the articles within that category.