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 DemoFile
 {
-    public function resolve($item)
+    public function resolve(string $item)
     {
         return $item . ' world';
     }
 }

PHP snippet to change

<?php

final class DemoFile
{
    public function resolve($item)
    {
        return $item . ' world';
    }
}

Applied Rules:

StrictStringParamConcatRector

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\ClassMethod\StrictStringParamConcatRector;
use Rector\ValueObject\PhpVersion;

return RectorConfig::configure()
    ->withRules([
        // 'string' type declaration is not available in PHP version 5.6 or earlier
        StrictStringParamConcatRector::class
    ])
    // specific PHP version
    ->withPhpVersion(PhpVersion::PHP_54);

Rector version: 2.4.2 - released at 2026-04-16 14:00