?>
    <?php 
        $letter = trim($letter);
        $disabledClass = null;
        $activeClass = null;
        if ($availLetter[$i] != true) {
            $disabledClass = ' disabled';
        }
        if ($this->char == $letter) {
            $activeClass = ' active';
        }
        ?>
        <li>
        <a<?php 
        if ($availLetter[$i] != false && $this->char != $letter) {
            echo ' href="' . JRoute::_(TZ_Portfolio_PlusHelperRoute::getLetterRoute('portfolio', $letter)) . '"';
        }
        ?>
           class="btn-sm<?php 
        echo $disabledClass . $activeClass;
        ?>
"><?php 
        echo mb_strtoupper(trim($letter));
        ?>
</a>
        </li>
  <?php 
    }
}
?>
</ul>