app/Template/external_task_modification/show.php

<form method="post" action="<?= $this->url->href('TaskModificationController', 'update', array('task_id' => $task['id'])) ?>">
    <?= $this->form->csrf() ?>
    <?= $this->form->hidden('id', $values) ?>
    <?= $this->form->hidden('project_id', $values) ?>

    <?php if (! empty($error_message)): ?>
        <p class="alert alert-error"><?= $this->text->e($error_message) ?></p>
    <?php else: ?>
        <?= $this->render($template, array(
            'project' => $project,
            'task' => $task,
            'external_task' => $external_task,
            'tags' => $tags,
            'users_list' => $users_list,
            'categories_list' => $categories_list,
            'values' => $values,
            'errors' => $errors,
        )) ?>
    <?php endif ?>

    <?= $this->modal->submitButtons() ?>
</form>