php artisan admin:install

PHP Fatal error:  Cannot use 'String' as class name as it is reserved in      /var/www/projects/blog.laravel.com/vendor/sleeping-owl/admin/src/SleepingOwl/Admin/Columns/Column/String.php on line 3
[SymfonyComponentDebugExceptionFatalErrorException]
Cannot use 'String' as class name as it is reserved

<?php namespace SleepingOwlAdminColumnsColumn;

     class String extends BaseColumn
        {... }

php artisan sleepingowl:install

[ErrorException]
Invalid argument supplied for foreach()