how to add $post->ID to nocache_headers()

Hi all,

I’m new to wordpress development and I tried for couple of days to make this work without much success.

What I want to achieve is to add a custom header with post url as a value when a new post is published or a new comment to that post is added. I’ve seen that for this the nocache_headers() function is used, so I tried to use it like this

$permalink = get_permalink($post->ID);
nocache_headers($permalink)

then, of course, I have changed the actual functions to be like the following (from the wp-includes/functions.php file, changes are in bold):

/**
 * Gets the header information to prevent caching.
 *
 * The several different headers cover the different ways cache prevention is handled
 * by different browsers
 *
 * @since 2.8.0
 *
 * @uses apply_filters()
 * @return array The associative array of header names and field values.
 */
function wp_get_nocache_headers(<strong>$permalink</strong>) {
        $headers = array(
                'Expires' => 'Wed, 11 Jan 1984 05:00:00 GMT',
                'Cache-Control' => 'no-cache, must-revalidate, max-age=0',
                'Pragma' => 'no-cache',
                <strong>'MyHeader' => $permalink</strong>
        );

        if ( function_exists('apply_filters') ) {
                $headers = (array) apply_filters('nocache_headers', $headers);
        }
        $headers['Last-Modified'] = false;
        return $headers;
}

/**
 * Sets the headers to prevent caching for the different browsers.
 *
 * Different browsers support different nocache headers, so several headers must
 * be sent so that all of them get the point that no caching should occur.
 *
 * @since 2.0.0
 * @uses wp_get_nocache_headers()
 */
function nocache_headers(<strong>$permalink</strong>) {
        $headers = wp_get_nocache_headers(<strong>$permalink</strong>);

        unset( $headers['Last-Modified'] );

        // In PHP 5.3+, make sure we are not sending a Last-Modified header.
        if ( function_exists( 'header_remove' ) ) {
                @header_remove( 'Last-Modified' );
        } else {
                // In PHP 5.2, send an empty Last-Modified header, but only as a
                // last resort to override a header already sent. #WP23021
                foreach ( headers_list() as $header ) {
                        if ( 0 === stripos( $header, 'Last-Modified' ) ) {
                                $headers['Last-Modified'] = '';
                                break;
                        }
                }
        }

        foreach( $headers as $name => $field_value )
                @header("{$name}: {$field_value}");
}

as a result the custom header is created, but it is empty without any value, so I’m wondering what I’m doing wrong here?
I have tried also with

global $post;
$permalink = get_permalink($post->ID);
nocache_headers($permalink)

and got the same result.

Any help is greatly appreciated, or any other method to achieve the above.

Thanks!