forms_bundle/index.php

<?php

require_once __DIR__ . "/vendor/autoload.php";

$form = new \itguild\forms\ActiveForm();
$form->beginForm("/some_action");
$form->field(class: \itguild\forms\inputs\File::class, name: "login", params: [
    'class' => "form-control",
    'placeholder' => 'Файл',
    ])
    ->setLabel("Файл")
    ->setMultiple()
    ->render();

$form->endForm();