functions.php

<?php
/**
 * Multiple Authors in DPS
 * @see https://displayposts.com/2019/01/04/display-multiple-authors-using-co-authors-plus/
 */
function be_multiple_authors_in_dps( $output = '', $original_atts = array() ) {
	if( ! function_exists( 'coauthors' ) )
		return $output;
	$atts = shortcode_atts( array( 
		'coauthor_function'     => 'coauthors',
		'coauthor_between'      => ', ',
		'coauthor_between_last' => ' and ',
		'coauthor_before'       => 'by ',
		'coauthor_after'        => '',
	), $original_atts, 'dps-coauthor-addon' );
	
	$function     = in_array( $atts['coauthor_function'], array( 'coauthors', 'coauthors_posts_links', 'coauthors_links' ) ) ? $atts['coauthor_function'] : 'coauthors';
	$between      = esc_html( $atts['coauthor_between'] );
	$between_last = esc_html( $atts['coauthor_between_last'] );
	$before       = esc_html( $atts['coauthor_before'] );
	$after        = esc_html( $atts['coauthor_after'] );
	$echo         = false;
	
	return ' <span class="author">' . call_user_func_array( $function, array( $between, $between_last, $before, $after, $echo ) ) . '</span>';
}