$countries = ['russia' => 'Россия', 'neverland' => 'Небыляндия'];
foreach($countries as $key => $value){
echo "<option value=\"{$key}\">{$value}</option>";
}
$selected = [];
foreach($_POST["country"] as $country) {
$selected[] = $countries[$country];
}
$email_content .= implode(', ', $selected);
<?php $query = new WP_Query(array(
'post_type' => 'partners',
'posts_per_page' => -1
));
$post_in_page = array_chunk($query->posts,4);
if ($query->have_posts()) :?>
<ul class="bxslider-partners partners-slide">
<?php foreach ($post_in_page as $_posts) : ?>
<li>
<?php foreach($_posts as $pst): ?>
$img = get_field('img_partners',$pst->ID);
?>
<div class="img-block-slide">
<img src="<?php echo $img; ?>" alt="<?php echo $pst->post_title?>">
</div>
<?php endforeach;?>
</li>
<?php endforeach;?>
</ul>
<?php endif;?>