Deprecated: preg_replace(): The /e modifier is deprecated

RegisterKernelListenersPass.php

$event['method'] = 'on'.preg_replace(array(
                        '/(?<=\b)[a-z]/ie',
                        '/[^a-z0-9]/i'
                    ), array('strtoupper("\\0")', ''), $event['event']);
                    
                    
                    replace with
                    
$event['method'] = 'on'.preg_replace_callback(array(
             '/(?<=\b)[a-z]/i',
             '/[^a-z0-9]/i',
             ), function ($matches) { return strtoupper($matches[0]); }, $event['event']);
             $event['method'] = preg_replace('/[^a-z0-9]/i', '', $event['method']);