Trouble with WP_Query

Like this:
$loop2 = new WP_Query( 'posts_per_page' => 8 );
or
$loop2 = new WP_Query( 'posts_per_page=8' );
…WordPress Codex : Class Reference/WP Query

NeoTechnomad, I tried this code and it display all posts, not only 8 but ALL. Why? this is a bug? or I need some other config options?

Try:
$loop2_query = new WP_Query( 'posts_per_page' => 8 );
or
$loop2_query = new WP_Query( 'posts_per_page=8' );
Pagination Parameters

This is directly from my dev site where I use multiple WP_query…

<?php $the_query = new WP_Query( 'posts_per_page=3' ); ?>
<?php if ( $the_query->have_posts() ) : while ( $the_query->have_posts() ) : $the_query->the_post(); ?>

	<div id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
		<h2><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h2>
		<?php if ( has_post_thumbnail() ) {
			the_post_thumbnail();
		} ?>
		<?php echo excerpt(30); ?>
	</div>

<?php endwhile; ?>
<?php wp_reset_query(); ?>
<?php endif; ?>

example of my loop

<?php
$the_query = new WP_Query('posts_per_page=8');?>
<ul class="latestpost">
<?php if ($the_query->have_posts()): ?>
<?php while ($the_query->have_posts()) : $the_query->the_post(); ?>
<li>                       						   <?php if(has_post_thumbnail()) { ?>
<?php
$thumb = get_post_thumbnail_id();
$img_url = wp_get_attachment_url( $thumb,'full'); //get img URL
$image = aq_resize( $img_url, 211, 158, true ); //resize & crop img
?>
<figure class="featured-thumbnail-rel">
    <a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>
    <img src="<?php echo $image ?>" alt="<?php the_title(); ?>" /></a>
</figure>
<?php } ?>
<h2><a href="<?php the_permalink(); ?>"><?php the_title(''); ?></a></h2>
<div class="excerpt"><?php $excerpt = get_the_excerpt(); echo my_string_limit_words($excerpt,26);?></div>
<div class="link"><a href="<?php the_permalink(); ?>">Читать далее</a></div>
</li>
<?php endwhile; ?>
<?php wp_reset_query(); ?>
<?php endif; ?>
</ul>

and this loop doesn`t work as I expected ?? I think this happens cause I use multiple loop on my front page.
But why when I add a ‘cat’ parameter loop works nice?

There were several minor errors in the code. This should work…

<?php $the_query = new WP_Query( 'posts_per_page=8' ); ?>
<ul class="latestpost">
	<?php if ($the_query->have_posts()): while ($the_query->have_posts()) : $the_query->the_post(); ?>
	<li>
		<?php
			$thumb = get_post_thumbnail_id();
			$img_url = wp_get_attachment_url( $thumb,'full'); //get img URL
			$image = aq_resize( $img_url, 211, 158, true ); //resize & crop img
		?>
		<figure class="featured-thumbnail-rel">
			<a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>
			<img src="<?php echo $image ?>" alt="<?php the_title(); ?>" />
			</a>
		</figure>

		<h2>
			<a href="<?php the_permalink(); ?>">
				<?php the_title(); ?>
			</a>
		</h2>

		<div class="excerpt">
			<?php $excerpt = get_the_excerpt(); echo my_string_limit_words( $excerpt, 26 ); ?>
		</div>
		<div class="link">
			<a href="<?php the_permalink(); ?>">
				<?php the_title(); ?>
			</a>
		</div>
	</li>
	<?php
	endwhile;
	wp_reset_query();
	endif;
	?>
</ul>

For multiple loops, read: WordPress Codex : The Loop > Multiple Loops

I create special page for your example of loop and have the same behaviour ??

https://express-kirov.ru/test/

This page displays all posts, ignoring the ‘posts_per_page=8’ option