PHP Group array by first letter

first-letter-group.php

<?php if (!empty($items)): ?>
    <ul>
        <?php $current_letter = ''; ?>
        <?php foreach ($items as $item) : ?>
            <?php $first_letter = mb_substr($item['post_title'], 0, 1, "UTF-8"); ?>
            <?php if ($first_letter != $current_letter) : ?><li><?php endif;  // group list ?>
                <?php if ($first_letter != $current_letter) : ?>
                    <h2><?php echo $first_letter; ?></h2>
                    <?php $current_letter = $first_letter; ?>
                <?php endif; ?>
                <p class="mb5"><?php echo $item['post_title'];?></p>
            <?php if ($first_letter != $current_letter) : ?></li><?php endif; // group list ?>
        <?php endforeach; ?>
    </ul>
<?php endif; ?>

Many Thanks for this!