PregReplaceEModifierRector

The /e modifier is no longer supported, use preg_replace_callback instead

 class SomeClass
 {
     public function run()
     {
-        $comment = preg_replace('~\b(\w)(\w+)~e', '"$1".strtolower("$2")', $comment);
+        $comment = preg_replace_callback('~\b(\w)(\w+)~', function ($matches) {
+              return($matches[1].strtolower($matches[2]));
+        }, $comment);
     }
 }

Configure your rector.php:

<?php

use Rector\Config\RectorConfig;
use Rector\Php55\Rector\FuncCall\PregReplaceEModifierRector;

return RectorConfig::configure()
    ->withRules([
        PregReplaceEModifierRector::class,
    ]);
SETS:  PHP 5.5