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:

 
 final class CarIdentifierNoResult
 {
-    private ?string $body;
+    private readonly ?string $body;
     
     /**
      * @param Baureihe|null         $modelSeries

PHP snippet to change

<?php

namespace tracking;

class Baureihen {
    public bool $karosserie;
}

final class CarIdentifierNoResult
{
    private ?string $body;
    
    /**
     * @param Baureihe|null         $modelSeries
     */
    public function __construct(
        $modelSeries,
    ) {
        $this->body = $modelSeries ? $modelSeries->karosserie : null;
    }
}

Applied Rules:

ReadOnlyPropertyRector

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\Php81\Rector\Property\ReadOnlyPropertyRector;
use Rector\ValueObject\PhpVersion;

return RectorConfig::configure()
    ->withRules([
        ReadOnlyPropertyRector::class
    ])
;

Rector version: 3b8b78 - released at 2026-07-24 13:03