需要显示3个帖子。我创建了以下代码：

add_shortcode(\'projects\', \'projects_shortcode\');
function projects_shortcode($atts, $content){

extract(shortcode_atts(array(
        \'post_type\' => \'project\',
        \'post_status\'       => \'publish\',
        \'posts_per_page\' => 3,
        \'caller_get_posts\' => 1
    ), $atts));

$args = array(
    \'post_type\'         => $post_type,
    \'post_status\'       => $post_status,
    \'posts_per_page\'    => $posts_per_page
);

global $post;

$posts = new WP_Query($args);
$out = \'\';
if ($posts->have_posts())
    while ($posts->have_posts()):
        $posts->the_post();

        $overview_image = get_field(\'small_overview_image\');

        $out = \'<div class="row"><div class="col-md-4">
                <a href="\'.get_permalink().\'" title="\' . get_the_title() . \'" class="project-item">                    
                <div class="project-item_img"><img class="img-fluid" src="\'.$overview_image[\'url\'].\'" /></div>
                <div class="project-item_title">
                <div class="project-item_title-name">\'.get_the_title().\'</div> 
                <div class="project-item_title-description">\'.get_the_title().\'</div></div>\';
        $out .=\'</a></div></div>\';
        /* these arguments will be available from inside $content
            get_permalink()
            get_the_content()
            get_the_category_list(\', \')
            get_the_title()
            and custom fields
            get_post_meta($post->ID, \'field_name\', true);
        */
    endwhile;
else
    return; // no posts found

wp_reset_query();
return html_entity_decode($out);
}

但此代码仅显示1个帖子。\'posts_per_page\' => 3 不工作。我不是php开发人员。此代码中哪里可能有错误？