WordPress Custom RSS feed

custom-feed.php

<?php
/*
Plugin Name: Custom RSS Feed for App
Description: A plugin creating a customized rssfeed
Plugin URI: https://urre.me/
Author: Urban Sandén
Author URI: https://urre.me
*/

// Add dates for rss feed
function customfeed_rss_date( $timestamp = null ) {
	$timestamp = ($timestamp==null) ? time() : $timestamp;
	echo date(DATE_RSS, $timestamp);
}

// Add endpoint and specify EP mask
function customfeed_add_endpoint() {
	add_rewrite_endpoint( 'rssfeed', EP_PERMALINK | EP_PAGES );
}

add_action( 'init', 'customfeed_add_endpoint' );

// Check if /rssfeed is used
function customfeed_template_redirect() {
	global $wp_query;
	if ( ! isset( $wp_query->query_vars['rssfeed'] )  )
		return;
	customfeed_output_feed();
	exit;
}

add_action( 'template_redirect', 'customfeed_template_redirect' );

// Output rss feed
function customfeed_output_feed() {

	$postCount = 10;
	$postType = 'post';
	query_posts( array( 'post_type' => $postType, 'showposts' => $postCount ) );

	header('Content-Type: '.feed_content_type('rss-http').';charset='.get_option('blog_charset'), true);
	echo '<?xml version="1.0" encoding="'.get_option('blog_charset').'"?'.'>';

	?>

<rss version="2.0"
        xmlns:content="http://purl.org/rss/1.0/modules/content/"
        xmlns:wfw="http://wellformedweb.org/CommentAPI/"
        xmlns:dc="http://purl.org/dc/elements/1.1/"
        xmlns:atom="http://www.w3.org/2005/Atom"
        xmlns:sy="http://purl.org/rss/1.0/modules/syndication/"
        xmlns:slash="http://purl.org/rss/1.0/modules/slash/"
        <?php do_action('rss2_ns'); ?>>

		<channel>
			<title><?php bloginfo_rss('name'); ?> - Feed</title>
			<link><?php bloginfo_rss('url') ?></link>
			<atom:link href="http://dallas.example.com/rss.xml" rel="self" type="application/rss+xml" />
			<description>Nyheter från <?php echo get_bloginfo('name'); ?></description>
			<lastBuildDate><?php echo mysql2date('D, d M Y H:i:s +0000', get_lastpostmodified('GMT'), false); ?></lastBuildDate>
			<language><?php bloginfo_rss( 'language' ); ?></language>
<sy:updatePeriod><?php echo apply_filters( 'rss_update_period', 'hourly' ); ?></sy:updatePeriod>
        <sy:updateFrequency><?php echo apply_filters( 'rss_update_frequency', '1' ); ?></sy:updateFrequency>
        <?php do_action('rss2_head'); ?>

			<?php while(have_posts()) : the_post(); ?>

			<?php
				$image_src = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'large' );
				$image_alt = get_post_meta( get_post_thumbnail_id( $post->ID ), '_wp_attachment_image_alt', true );
				$posttags = get_the_tags($post->ID);

				?>
			<item>
				<title><?php echo html_entity_decode(get_the_title($post->ID)); ?></title>
				<link><?php echo get_permalink($post->ID); ?></link>
				<description>
				<?php if ( has_post_thumbnail( $post->ID ) ) :
							echo '<![CDATA[<img src="' . $image_src[0] . '" height="600" width="1024" alt="' . $image_alt . '">]]>';
				endif; ?>
				<?php echo '<![CDATA[<p>Etiketter: </p>]]>'; ?>
				<?php if ($posttags) : foreach($posttags as $tag) : echo '<![CDATA[<a href="' .  get_tag_link($tag->term_id) . '">' . $tag->name . '</a>]]>'; endforeach; endif; ?>
				</description>
 				<content:encoded><![CDATA[<?php echo the_content() ?>]]></content:encoded>
    		<?php rss_enclosure(); ?>
        <?php do_action('rss2_item'); ?>

				<pubDate><?php customfeed_rss_date( strtotime($post->post_date_gmt) ); ?></pubDate>
				<dc:creator><?php echo get_the_author($post->ID); ?></dc:creator>
				<guid><?php echo get_permalink($post->ID); ?></guid>
			</item>
			<?php endwhile; ?>
	</channel>
</rss>
<?php
}

function customfeed_activate() {
	customfeed_add_endpoint();
	flush_rewrite_rules();
}

register_activation_hook( __FILE__, 'customfeed_activate' );

function customfeed_deactivate() {
	flush_rewrite_rules();
}

register_deactivation_hook( __FILE__, 'customfeed_deactivate' );