yii2/extensions/gii/views/default/diff.php

<?php
/**
 * @var yii\web\View $this
 * @var mixed $diff
 */
?>
<div class="default-diff">
	<?php if ($diff === false): ?>
		<div class="alert alert-danger">Diff is not supported for this file type.</div>
	<?php elseif (empty($diff)): ?>
		<div class="alert alert-success">Identical.</div>
	<?php else: ?>
		<div class="content"><?= $diff ?></div>
	<?php endif; ?>
</div>