<?php

/**
 * Add support for serial commas to Co-Authors Plus WordPress plugin.
 *
 * Filters coauthors_default_between_last to support serial commas, aka oxford commas, for 3 or more coauthors
 * ex:  By Samantha Larson, Darby Minow Smith, and David Roberts
 * ex:  By Samantha Larson and Darby Minow Smith
 */
add_filter( 'coauthors_default_between_last', function( $between_last ) {
	// only be concerned with commas with ' and ' which is CAP's default value
	if ( ' and ' !== $between_last )
		return $between_last;
	// prefix a comma if there are more than two coauthors
	$coauthors = get_coauthors();
	if ( count( $coauthors ) > 2 )
		return ', and ';
	else
		return ' and ';
});