Create an easy String using php function.

$new = array('a','b','c','d','e','f');
$comma_list = strrev(implode(strrev(' and'), explode(strrev(','), strrev(implode(', ', $new)), 2)));
echo 'The list is ' . $comma_list . '.';

output:
The list is a,b,c,d,e and f.