<?php if ($lastChar !== ($currentChar = mb_convert_case(mb_substr($row['category_name'], 0, 1), CASE_UPPER))): ?>
<?php $lastChar = $currentChar; ?>
<h1 class="bukva" id="bukva_<?= mb_convert_case($lastChar, CASE_LOWER); ?>"><?= $lastChar; ?></h1>
<?php endif; ?>
