Organize Series and organize-series-multiples: allowing for post links for posts that belong to multiple series to have a context saved when clicked from series archive page. This doesn't work as is - gonna move to the main file and fix.

modify_series_post_links_by_context.php

<?php
add_filter('init', 'modify_series_link_context');

function modify_series_link_context() {
	add_filter('post_link', 'multi_series_link_mod', 10, 3);
	add_filter('get_the_series', 'multi_series_get_mod');
}

function multi_series_link_mod($permalink, $post, $leavename) {
	//is the displayed page a series archive page?  If so, then let's make sure we append a request variable to the post links for this series.
	$new_link = $permalink;
	if ( is_series() ) { 
		$series_id = get_query_var(SERIES_QUERYVAR);
		if ( !is_numeric($series_slug) ) {
			$series_id = get_term_by('name', htmlentities2($series_id), 'series');
		}
		
		if ( empty($series_id) ) 
			return false; //get out we need a series id

		$new_link = add_query_arg('ref_ser', $series_id, $permalink);
	}

	//k now let's see if we've been referred by a series archive page
	if ( $ref_ser = get_query_var('ref_ser') ) {
		$series_id = $ref_ser;
		$new_link = add_query_arg('ref_ser', $series_id, $permalink);
	}

	return $new_link;
}

function multi_series_get_mod($series) {
	//let's filter drop any series that don't match the series_id (if present) in the $_REQUEST array
	if ( $ref = get_query_var('ref_ser') ) {
		$series_id = $ref_ser;
		if ( $series->term_id != $ref_ser ) 
			return false;
	}

	return $series;
}

?>