Page template to create RSS campaigns with WordPress and Mailchimp

tpl-rss-feed-for-mailchimp.php

<?php
/*
Template Name: Custom RSS Feed
*/

$numposts = 5;
$numchars = 300;
$thumbformat = 'medium';
$alt_text = 'Klik hier voor de afbeelding...';


function the_excerpt_max_charlength($excerpt, $charlength) {
	$charlength++;
	$str = '';
	if ( mb_strlen( $excerpt ) > $charlength ) {
		$subex = mb_substr( $excerpt, 0, $charlength - 5 );
		$exwords = explode( ' ', $subex );
		$excut = - ( mb_strlen( $exwords[ count( $exwords ) - 1 ] ) );
		if ( $excut < 0 ) {
			$str .= mb_substr( $subex, 0, $excut );
		} else {
			$str .= $subex;
		}
		$str .= '...';
	} else {
		$str .= $excerpt;
	}
	return $str;
}

$posts = query_posts(array('posts_per_page' => $numposts));

$lastdate = date(DATE_RSS, strtotime($posts[0]->post_modified_gmt) );

header("Content-Type: application/rss+xml; charset=UTF-8");
echo '<?xml version="1.0"?>
<rss version="2.0" xmlns:media="http://search.yahoo.com/mrss">
<channel>
	<title>'.get_option('blogname').' RSS Updates</title>
	<link>'.get_option('home').'</link>
	<description>The latest blog posts from '.get_option('blogname').'.</description>
	<language>'.strtolower(get_bloginfo('language')).'</language>
	<pubDate>'.$lastdate.'</pubDate>
	<lastBuildDate>'.$lastdate.'</lastBuildDate>
	<managingEditor>'.get_option('admin_email').'</managingEditor>';
foreach ($posts as $post) { 
    setup_postdata( $post );
    $excerpt = get_the_excerpt();
    echo '
	<item>
		<title>'.get_the_title().'</title>
		<link>'.get_permalink().'</link>
		<description><![CDATA['.the_excerpt_max_charlength($excerpt, $numchars).']]></description>
		<pubDate>'.date(DATE_RSS, strtotime(get_the_date())).'</pubDate>';
    if (get_the_post_thumbnail()) {
        $img = wp_get_attachment_image_src(get_post_thumbnail_id(), $thumbformat);
        echo '
        <media:content url="'.$img[0].'" medium="image" description="'.$alt_text.'"/>';
    }
    echo '
        <guid>'.get_permalink().'</guid>
	</item>';
} 
wp_reset_postdata();
echo '
</channel>
</rss>';

Place this template file into your theme directory and create a simple page without any content.
Tip! Use Yoast SEO's "noindex" feature and exclude that page from Google.