Nesting a PHP Array or Laravel Collection Recursively Based on parentId

Learn how to effortlessly nest PHP arrays or Laravel collections by matching `id` and `parentId` values. Transform your flat data structure into a hierarchical format!
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This video is based on the question https://stackoverflow.com/q/66476312/ asked by the user 'Even' ( https://stackoverflow.com/u/15329775/ ) and on the answer https://stackoverflow.com/a/66476474/ provided by the user 'Hossein Piri' ( https://stackoverflow.com/u/6150336/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Mastering Nested PHP Arrays and Laravel Collections

In web development, dealing with structured data can often present challenges. One common issue developers encounter is how to correctly nest a PHP array or a Laravel collection based on related values, such as parentId. This post will walk you through an efficient solution to this problem, whether you're working with a Laravel collection or a standard PHP array.

Understanding the Problem

Imagine you have a flat array consisting of categories and their subcategories. Each item in the array represents an element with an id, a title, and a parentId that links it to its parent category. The goal is to transform this flat structure into a nested format where each parent category includes its children.

Example Structure

Consider the following example array:

[[See Video to Reveal this Text or Code Snippet]]

In this example, each category has an id, a title, and a parentId. The parentId links subcategories to their respective parent categories. Categories with a parentId of 0 are top-level categories.

The Solution: Building the Nested Structure

To achieve the desired nested structure, we can create a recursive function that will traverse through the array and group the items based on their parentId.

Step-by-Step Breakdown

Define the Recursive Function

Create a function called buildTree() that will take two parameters: the elements to process and the current parentId. The default parent ID will be 0, indicating we start with top-level categories.

Initialize a Branch Array

Inside the function, initialize an empty array called $branch. This will hold the current level of categories being processed.

Iterate Over Elements

Loop through each element in the provided array. For each element:

Check if its parentId matches the current parentId.

If it does, call the same function recursively to find and add its children.

Once found, add the children key to the current element, and store it in the $branch array.

Return the Nested Structure

After iterating through all elements, return the $branch, which will now contain the nested structure.

The PHP Code

Here’s how you can implement this:

[[See Video to Reveal this Text or Code Snippet]]

Output Example

When you execute the buildTree() with the initial $foo array, you will get a nested array structured like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By implementing this recursive solution, you can transform a flat array into a hierarchical structure effortlessly. This technique is particularly useful in applications requiring structured data representation, like category systems or comment threads.

If you’re still using an older version of Laravel, like Laravel 5.1, this method will help you leverage the power of PHP to organize your data efficiently. Happy coding!

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