How to wrap every 3 posts in a div (and close the last div too) [closed]

Question

This is purely PHP which is considered to be Off-topic but this is my take:

<?php if ( have_posts() ) : ?>

    <?php
        while ( have_posts() ) :
            the_post();
            $i = $wp_query->current_post;
            echo ( 0 == $i % 3 ) ? '<div class="row">' : '';
    ?>

        <div class="project">
        </div> <!-- /.project -->

    <?php
            echo ( $wp_query->post_count == $i || 2 == $i % 3 ) ? '</div>' : '';
        endwhile;
    ?>

<?php endif; ?>

The $wp_query->current_post is a built-in query property that stats at 0 and holds the index of the posts array.