$arr = array('one' => 1, 'two' => 2, 'three' => 3);
$other = array('two', 'three');
var_dump(array_intersect_key($arr, array_flip($other)));
<li<?php if (!$_product->getDescription()): ?> class="active"<?php endif; ?>>
<a href="#tab-reviews" role="tab" data-toggle="tab">
<?php echo $this->__('Reviews') ?>
<?php Mage::getModel('review/review')->getEntitySummary($_product, Mage::app()->getStore()->getId()); ?>
<?php echo $reviewCount = $_product->getRatingSummary()->getReviewsCount() ? $_product->getRatingSummary()->getReviewsCount(): 0; ?>
</a>
</li>