Wordpress - Count on different loop - php

Question

How should I put count on this loop?
<?php
global $data;
$args = array('post_type' => 'post', 'posts_per_page' => $data['select_news']);
$loop = new WP_Query($args);
while ($loop->have_posts()) : $loop->the_post(); ?>
Someone can help me?
Thanks so much
Complete code:
<?php
global $data;
$args = array('post_type' => 'post', 'posts_per_page' => $data['select_news']);
$loop = new WP_Query($args);
while ($loop->have_posts()) : $loop->the_post(); ?>
<article class="article one-third column">
<div class="thumbnail">
<?php the_post_thumbnail('latest-news-thumb'); ?>
</div>
<h2><?php the_title(); ?><span>.</span></h2>
<div class="meta">
<span><?php _e('Postado em -', 'kula'); ?> <?php the_category(' & '); ?><br />on <strong><?php the_time('F jS, Y'); ?></strong></span>
<span><i class="icon-comment"></i> <?php $commentscount = get_comments_number(); echo $commentscount; ?> <?php _e('Comentários', 'kula'); ?></span>
</div>
<?php the_excerpt(); ?>
<a class="read-more-btn" href="<?php the_permalink() ?>"><?php _e('Leia mais', 'kula'); ?> <span>→</span></a>
</article><!-- end article -->
<?php endwhile; ?>
I need count 3 by 3 posts and put a class on article...
So i can put this code on article class:
<?php if (($count%3)==0) {echo ' last';}?>
Thanks

Answer 1

<?php
global $data;
$args = array('post_type' => 'post', 'posts_per_page' => $data['select_news']);
$loop = new WP_Query($args);
$totalPost = count($loop->posts); //will give total number of posts
?>
Edit:
This will insert last class in article after 3 posts
<?php
global $data;
$args = array('post_type' => 'post', 'posts_per_page' => $data['select_news']);
$loop = new WP_Query($args);
$postNo=0;
while ($loop->have_posts()) : $loop->the_post(); ?>
<article class="article one-third column <?php echo (($postNo++)%3==0)?' last ':'' ;?>">
<div class="thumbnail">
<?php the_post_thumbnail('latest-news-thumb'); ?>
</div>
<h2><?php the_title(); ?><span>.</span></h2>
<div class="meta">
<span><?php _e('Postado em -', 'kula'); ?> <?php the_category(' & '); ?><br />on <strong><?php the_time('F jS, Y'); ?></strong></span>
<span><i class="icon-comment"></i> <?php $commentscount = get_comments_number(); echo $commentscount; ?> <?php _e('Comentários', 'kula'); ?></span>
</div>
<?php the_excerpt(); ?>
<a class="read-more-btn" href="<?php the_permalink() ?>"><?php _e('Leia mais', 'kula'); ?> <span>→</span></a>
</article><!-- end article -->
<?php endwhile; ?>

Answer 2

After $loop = new WP_Query($args); use Sanjeev's suggestion i.e, $totalPost = count($loop->posts);

Answer 3

<?php
global $data;
$args = array('post_type' => 'post', 'posts_per_page' => $data['select_news']);
$loop = new WP_Query($args);
$count = 1; // add count variable
while ($loop->have_posts()) : $loop->the_post(); ?>
<article class="article one-third column<?php if (($count%3)==0) {echo ' last';}?>">
<!-- put your code here -->
</article>
<?php
$count++; //count ++
endwhile;
?>