Theme Files getting include in .ics downloaded file - php

Question

Im working on a simple script to include a "Add to calendar" button.
Im using the idea and ICS.php file from https://gist.github.com/jakebellacera/635416 that is a old post.
Im getting the file to download through a function using add_action( 'template_redirect', 'cl_download_ics' ); [The theme is Avada]. But what is happening now is that the download invite is including the themes template file to the file that I don't want and even after removing the template code that was added extra the file still does not want to add the event to the iCalendar.
Here is the code I have so var.
include_once (plugin_dir_path(__DIR__).'cl-add-to-calendar/ics.php');
function cl_download_ics(){
if (isset( $_GET['ics'])) {
$query_data_get = $_POST;
//$query_data = $query_data_get['calendar_data'];
$dtstart = date_create($query_data_get['date_start']);
$dtstart = date_format($dtstart,"Y/m/d H:i:s");
$dtend = date_create($query_data_get['date_end']);
$dtend = date_format($dtend,"Y/m/d H:i:s");
header('Content-Type: text/calendar; charset=utf-8');
header('Content-Disposition: attachment; filename=Invite.ics');
$ics = new ICS(array(
'location' => $query_data_get['location'],
'description' => $query_data_get['description'],
'dtstart' => $dtstart,
'dtend' => $dtend,
'summary' => $query_data_get['summary'],
'url' => $query_data_get['url']
));
echo $ics->to_string();
}
}
add_action( 'template_redirect', 'cl_download_ics' );
function calendar_btn_ad($atts){
// Shortcode atts with examples
// dtsrart --- 2017-1-16 9:00AM
// dtend --- 2017-1-16 9:00AM
// location --- 123 Fake St, New York, NY
// description --- This is my description
// summary --- This is my summary
// url --- http://example.com
$form_input_fields = array();
if (! empty($atts['dtsrart'])) {
$form_input_fields[] = '<input type="hidden" name="date_start" value="'.$atts['dtsrart'].'">';
};
if (! empty($atts['dtend'])) {
$form_input_fields[] = '<input type="hidden" name="date_end" value="'.$atts['dtend'].'">';
};
if (! empty($atts['location'])) {
$form_input_fields[] = '<input type="hidden" name="location" value="'.$atts['location'].'">';
};
if (! empty($atts['description'])) {
$form_input_fields[] = '<input type="hidden" name="description" value="'.$atts['description'].'">';
};
if (! empty($atts['summary'])) {
$form_input_fields[] = '<input type="hidden" name="summary" value="'.$atts['summary'].'">';
};
if (! empty($atts['url'])) {
$form_input_fields[] = '<input type="hidden" name="url" value="'.$atts['url'].'">';
};
$download_link = WP_PLUGIN_URL.'/cl-add-to-calendar/download-ics.php';
ob_start();
?>
<form action="?ics=true" method="post">
<?php foreach ($form_input_fields as $input_field): ?>
<?php echo $input_field; ?>
<?php endforeach; ?>
<input type="submit" id="cl-add-calendar-submit" value="Add to Calendar">
</form>
<div id="cl-btn-ajax-result">
</div>
<?php
$output = ob_get_clean();
return $output;
}
add_shortcode('cl_calendar_btn', 'calendar_btn_ad');

Answer 1

It is a feed, so add the feed using wordpress add_feed and your function. see
https://developer.wordpress.org/reference/functions/add_feed/.
function add_custom_feed() {
add_feed( 'ics', 'cl_download_ics' );
}
add_action( 'init', 'add_custom_feed' );
function cl_download_ics() {
header('Content-Type: text/calendar; charset=utf-8');
etc.....
}
I'm using custom post types for the event and adding the ics feed when I register the post type. Adding the feed needs to be done with an early wordpress action. Don't use theme actions.