ArrayValidator

use Fynix\Rule;

$validator = Rule::arrayOf('tags')
    ->min(1)
    ->max(5)
    ->each(Rule::string('tag')->length(2, 30));

$errors = $validator->validateFieldAll(['php', '']);

min() and max() constrain the item count. each() applies a validator to every item and reports errors using keys such as tags.1.