Laravel - how to group data by key and save to array?
Stefan Bogdanescu
Founder & Senior Architect · 2026-06-29
# Laravel: Grouping Data by Key and Saving to an Array – A Practical Guide
As senior developers working within the Laravel ecosystem, we frequently encounter data manipulation tasks where we need to transform relational database results into more usable structures, such as nested arrays. One common requirement is grouping related records based on a specific attribute (like `attr_group_id`) and pivoting the resulting values into an associative array.
This post will walk you through how to achieve this grouping efficiently using Laravel's capabilities, moving beyond simple manual loops to leverage the power of Eloquent and Collections, while also considering database-level optimization.
## The Problem: Pivoting Relational Data
Imagine we have a simple table structure: `attribute_values(id, value, attr_group_id)`. Our goal is to take this flat list and transform it into a nested array where each group ID contains an inner array mapping the record IDs to their values.
We want to transform:
`[ (1, 'one', 1), (2, 'two', 1), (3, 'three', 2), ... ]`
Into:
`[ 1 => [1 => 'one', 2 => 'two'], 2 => [3 => 'three', 4 => 'four'], ... ]`
While this transformation can be accomplished with basic PHP loops, a robust Laravel solution should strive for efficiency and readability.
## Method 1: The Manual Approach (Baseline)
Before diving into Laravel specifics, let’s look at the baseline approach using raw database results. This method is straightforward but less idiomatic in a modern framework environment.
```php
// Assuming $data is the result fetched from DB::table('attribute_values')->get()
$data = \DB::table('attribute_values')->get();
$attrs = [];
foreach ($data as $row) {
$group_id = $row->attr_group_id;
$record_id = $row->id;
$value = $row->value;
// Initialize the group if it doesn't exist
if (!isset($attrs[$group_id])) {
$attrs[$group_id] = [];
}
// Add the record ID and value to the specific group
$attrs[$group_id][$record_id] = $value;
}
return $attrs;
```
This approach works perfectly fine for small datasets. However, as your data scales, manually managing the initialization and assignment within a PHP loop can become verbose and less performant than leveraging built-in collection methods.
## Method 2: The Laravel Idiomatic Approach using Collections
Laravel excels at handling collections of data. By fetching the raw results into a Laravel Collection, we can utilize the powerful `groupBy()` method to handle the grouping operation cleanly. This approach is much cleaner and aligns better with the principles promoted by the Laravel team regarding data handling.
```php
use Illuminate\Support\Facades\DB;
// 1. Fetch all data using the Query Builder
$data = DB::table('attribute_values')->get();
// 2. Convert the results to a Collection for manipulation
$collection = collect($data);
// 3. Group the collection by 'attr_group_id'
$groupedData = $collection->groupBy('attr_group_id');
// 4. Transform the grouped collections into the desired nested array structure
$finalArray = [];
foreach ($groupedData as $group_id => $records) {
$nestedGroup = [];
// Within each group, pivot the 'id' and 'value' fields
foreach ($records as $record) {
$nestedGroup[$record->id] = $record->value;
}
$finalArray[$group_id] = $nestedGroup;
}
return $finalArray;
```
### Optimizing with Database Aggregation (The Performance Edge)
While the method above is clean in PHP, for very large datasets, performing this complex pivoting logic in PHP can introduce bottlenecks. The most performant solution often involves pushing the aggregation logic down to the database itself. Modern SQL databases, especially PostgreSQL or MySQL, offer powerful aggregation functions that can handle this transformation directly, resulting in significantly faster execution times.
For instance, using a combination of `JSON_ARRAYAGG` (in PostgreSQL) or similar features allows you to get the desired nested structure in a single query. This is often a more scalable pattern when dealing with heavy data retrieval, which is a core focus of best practices discussed on the official [Laravel documentation](https://laravelcompany.com).
## Conclusion
Grouping and pivoting relational data is a common challenge in application development. While direct PHP iteration works, leveraging Laravel's Collection methods like `groupBy()` provides a highly readable and maintainable solution for moderate datasets. For mission-critical performance, always explore the potential of your underlying SQL database to handle aggregations directly. By combining smart collection usage with efficient database query design, you ensure your Laravel applications remain fast, scalable, and robust.