crontab计划任务写法的优化

<?php
namespace process;

use Workerman\Crontab\Crontab;

class Task
{
    public function onWorkerStart()
    {
        new Crontab('* * * * * *', $this->abc());
    }

    public function abc() {
        return function() {
            echo "callback\n";
        };
    }

}

<?php
namespace process;

use Workerman\Crontab\Crontab;

class Task
{
    public function onWorkerStart()
    {
        new Crontab('* * * * * *', [$this, 'abc']);
    }

    public function abc() {
        return function() {
            echo "callback\n";
        };
    }

}