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             }
         }
 
-        foreach ($groups as $group) {
-            $thumbnails[] = $group;
-        }
+        $thumbnails = $groups;
         
         return $this->adminJson($thumbnails);
     }
 }

PHP snippet to change

<?php

final class DemoFile
{
    public function run(): JsonResponse
    {
        $thumbnails = [];
        $groups = [];
        $list = new DemoList();
        foreach ($list->getItems() as $item) {
            if ($item->hasGroup()) {
                $groups[] =['id' => $item->getName()];
            } else {
                $thumbnails[] = ['id' => $item->getName()];
            }
        }

        foreach ($groups as $group) {
            $thumbnails[] = $group;
        }
        
        return $this->adminJson($thumbnails);
    }
}

Applied Rules:

ForeachItemsAssignToEmptyArrayToAssignRector

Not a change you expect?

Create an issue on GitHub
...or to speed up fix – add a test fixture

Config rector.php

<?php

use Rector\Config\RectorConfig;
use Rector\ValueObject\PhpVersion;

return RectorConfig::configure()
    ->withPreparedSets(typeDeclarations: true)
    ->withPhpVersion(PhpVersion::PHP_83)
    ->withPhpSets(php83: true)
    ->withPreparedSets(deadCode: true, codeQuality: true, earlyReturn: true)
    ;

Rector version: eac1ef - released at 2026-02-01 16:47