<?php
extract(shortcode_atts(array(
    'interval' => '',
    'el_class' => '',
), $atts));
$el_class = $this->getExtraClass($el_class);
$is_rotate = ($interval) ? 'true' : 'false';
?>
<div class="nt-testimonials carousel <?php echo $el_class; ?>" data-items="1" data-single-item="true" data-transition-style="fade" data-nav="true" data-autoplay="<?php echo $is_rotate; ?>" data-autoplay-timeout="<?php echo $interval; ?>" data-loop="true" data-auto-height="true" data-dots="false" data-autoplay-hover-pause="true" data-autoplay-speed="1000" data-animate-out="fadeOut" data-animate-in="fadeIn">
<?php echo do_shortcode($content); ?>
</div>