Auto set featured image for post by random

auto-set-featured-image-for-post-by-random

<?php

$begin_ID = 1;
$end_ID = 10;

$items = array();

for ($i = $begin_ID; $i <= $end_ID; $i++) {
    $items[] = $i;
}

$posts = new WP_Query(array(
    'post_type' => array('post'),
    'posts_per_page' => -1
));

$index = 0;

while ($posts->have_posts()){
    $posts->the_post();
    set_post_thumbnail(get_the_ID(), $items[$index]);
    if ($index == count($items) - 1)
        $index = 0;
    else
        $index++;
}

wp_reset_postdata();

You can read full tutorial on my blog http://colourstheme.com/2015/01/auto-set-featured-image-for-post-by-random/