Indexing a PHP array of objects by their class name

Published on 2023-06-17 • Modified on 2023-06-17

This snippet shows how to index a PHP array of objects by their class name. We can use the array_reduce function instead of doing a loop. Note that you can only do this if you are sure you don't have several objects of the same class. To be sure it's not the case, you can verify that the count is identical for both arrays.

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<?php

declare(strict_types=1);

namespace App\Controller\Snippet;

use App\Samples\OrderPlacedEvent;
use App\Samples\ProductSample;
use App\Samples\SortableObject;

/**
 * I am using a PHP trait to isolate each snippet in a file.
 * This code should be called from a Symfony controller extending AbstractController (as of Symfony 4.2)
 * or Symfony\Bundle\FrameworkBundle\Controller\Controller (Symfony <= 4.1).
 * Services are injected in the main controller constructor.
 */
trait Snippet261Trait
{
    public function snippet261(): void
    {
        $objects = [
            new ProductSample(),
            new OrderPlacedEvent(),
            new SortableObject('foo'),
            // new SortableObject('bar'),
        ];
        var_dump($objects);

        $indexedByClass = array_reduce($objects, static function ($carry, $item) {
            $carry[\get_class($item)] = $item; // @phpstan-ignore-line

            return $carry;
        }, []);

        var_dump($indexedByClass);

        var_dump($indexedByClass[OrderPlacedEvent::class]);

        if (\count($objects) === \count($indexedByClass)) {
            echo PHP_EOL."The array doesn't contain duplicates of the same class.";
        }

        // That's it! 😁
    }
}

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