Try Rector Online | Rector - Automated Way to Instantly Upgrade and Refactor any PHP code

Run Rector on your code to see what it can do for you:

 <?php
 
-$result = array_map(array: $items, callback: fn ($item) => $item * 2);
+$result = array_map(array: $items, callback: fn ($item): int|float => $item * 2 array: $items, callback: fn ($item) => $item * 2);

PHP snippet to change

<?php

$result = array_map(array: $items, callback: fn ($item) => $item * 2);

Applied Rules:

AddArrowFunctionReturnTypeRector

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\TypeDeclaration\Rector\Property\TypedPropertyFromAssignsRector;
use Rector\ValueObject\PhpVersion;

return RectorConfig::configure()
    // A. whole set
    ->withPreparedSets(typeDeclarations: true)
    // B. or few rules
    ->withRules([
        TypedPropertyFromAssignsRector::class
    ])
    // demonstrate specific PHP version
    ->withPhpVersion(PhpVersion::PHP_84);

Rector version: bb186b - released at 2026-06-19 00:08