helper-functions.php

<?php

/**
 * Join Multiple Items
 * Separate last two items by 'and', remaining by commas
 * Ex: item 1, item 2 and item 3
 */
function ea_join_multiple( $items ) {

	if ( empty( $items ) ) {
		$output = '';

	} elseif ( 1 == count( $items ) ) {
		$output = $items[0];

	} else {
		// Combine all but last partial using commas.
		$output = implode( ', ', array_slice( $items, 0, -1 ) );
		// Add 'and' separator.
		$output .= ' and ';
		// Add last partial.
		$output .= end( $items );
	}

	return $output;	
}