This function turns an array into a nice list, with list items wrapped in custom strings, separated with commas, with "and" before the final item.

nice_list.php

<?php

function nice_list($items, $wrapper = false) {
    if($wrapper) {
        $wrapper = str_split($wrapper, strlen($wrapper) / 2);
        foreach($items as &$item) {
            $item = $wrapper[0].$item.$wrapper[1];
        }
    }
    if(count($items) == 1) return $items[0];
    if(count($items) == 2) return $items[0].' and '.$items[1];
    $last = array_pop($items);
    array_push($items, 'and '.$last);
    return implode(', ', $items);
}

$items[] = 'pebble';
$items[] = 'bean';
$items[] = 'peanut';
$items[] = 'marble';
$items[] = 'paperclip';

echo nice_list($items, '[[]]'); // [[pebble]], [[bean]], [[peanut]], [[marble]], and [[paperclip]]

Check out this gist for a simpler version of the function that doesn't support custom string wrapping.