Laravel 5.* modify column with migration

I have follow the laravel migration steps and its good. My problem is about on modifying the column. I already installed the doctrine\dbal in composer. But when i change the column $table->string('name')->nullable()->change() with change method, then run php artisan migrate. Is says nothing to migrate. Why? Do i need to use the doctrin\dbal like this use Doctine\dbal in the migration table class? Or what is the better way to implement for modifying the table column in migration and what artisan should i run? Any help please!

via Chebli Mohamed