Given an array of 0 or more values, pretty_join() will concatenate all of the values together using a common delimiter (a comma by default) except for the last two values which will be joined by the final separator (an ampersand by default).

pretty_join.php

<?php
function pretty_join($array, $intermediate_separator = ', ', $final_separator = ' & ')
{
  if (!is_array($array)) return null;
  switch (sizeof($array))
  {
    case 0: return null; break;
    case 1: return reset($array); break;
    case 2: return implode($final_separator, $array); break;
    default:
      $end = array_pop($array);
      // This second call prevents the last two elements from being reversed
      $end = array_pop($array) . $intermediate_separator . $final_separator . $end;
      array_push($array, $end);
      return implode($intermediate_separator, $array);
  }
}
?>

pretty_join_examples.php

<?php
//pretty_join with 0 elements
echo pretty_join(array());
// =>
//pretty_join with 1 elements
echo pretty_join(array('Big Tires'));
// => Big Tires
//pretty_join with 2 elements
echo pretty_join(array('Big Tires', 'Pretty Houses'));
// => Big Tires & Pretty Houses
//pretty_join with 3 elements
echo pretty_join(array('Big Tires', 'Pretty Houses', 'Fat Wives'));
// => Big Tires, Pretty Houses, & Fat Wives
?>