[] => array()

ecs.php

<?php

declare(strict_types=1);

use PhpCsFixer\Fixer\ArrayNotation\ArraySyntaxFixer;
use Symplify\EasyCodingStandard\Config\ECSConfig;

return ECSConfig::configure()
    ->withConfiguredRule(ArraySyntaxFixer::class,
        array('syntax' => 'long')
    );