Need a regex to add css class to first and last list item

$patterns = array('/<ul+([^<]*)<li/m', '/<([^<]*)(?<=<li)(.*)</ul>/s');
    $replace = array('<ul$1<li class="first"','<li class="last"$2$3</ul>');
    $navigation = preg_replace($patterns, $replace, $navigation);

$(document).ready(
    function() {
        $('#id-of-ul:firstChild').addClass('first');
        $('#id-of-ul:lastChild').addClass('last');
    }

);

$patterns = array('/<ul+([^<]*)<li/m','/<([^<]*)(?<=<li)(.*)</ul>/s');

<?php
$navigation='<ul>
<li>Coffee</li>
<li>Tea</li>
<li>Milk</li>
<li>Beer</li>
<li>Water</li>
</ul>';

$patterns = array('/<ul.*?>\s*<li/',
                  '/<li((.(?<!<li))*?<\/ul>)/s');
$replace = array('$0 class="first"',
                 '<li class="last"$1');
$navigation = preg_replace($patterns, $replace, $navigation);
echo $navigation;
?>

<ul>
<li class="first">Coffee</li>
<li>Tea</li>
<li>Milk</li>
<li>Beer</li>
<li class="last">Water</li>
</ul>

<?php
/**
 * Modify list items in pre-rendered html.
 *
 * Usage Example:
 *  $replaced_text = ListAlter::addClasses($original_html, array('cool', 'awsome'));
 */
class ListAlter {
  private $classes = array();
  private $classes_found = FALSE;
  private $count = 0;
  private $total = 0;

  // No public instances.
  private function __construct() {}

  /**
   * Adds 'first', 'last', and any extra classes you want.
   */
  static function addClasses($html, $extra_classes = array()) {
    $instance = new self();
    $instance->classes = $extra_classes;
    $total = preg_match_all('~<li([^>]*?)>~', $html, $matches);
    $instance->total = $total ? $total : 0;
    return preg_replace_callback('~<li([^>]*?)>~', array($instance, 'processListItem'), $html);
  }

  private function processListItem($matches) {
    $this->count++;
    $this->classes_found = FALSE;
    $processed = preg_replace_callback('~(w+)="(.*?)"~', array($this, 'appendClasses'), $matches[0]);
    if (!$this->classes_found) {
      $classes = $this->classes;
      if ($this->count == 1) {
        $classes[] = 'first';
      }
      if ($this->count == $this->total) {
        $classes[] = 'last';
      }
      if (!empty($classes)) {
        $processed = rtrim($matches[0], '>') . ' class="' . implode(' ', $classes) . '">';
      }
    }
    return $processed;
  }

  private function appendClasses($matches) {
    array_shift($matches);
    list($name, $value) = $matches;
    if ($name == 'class') {
      $value = array_filter(explode(' ', $value));
      $value = array_merge($value, $this->classes);
      if ($this->count == 1) {
        $value[] = 'first';
      }
      if ($this->count == $this->total) {
        $value[] = 'last';
      }
      $value = implode(' ', $value);
      $this->classes_found = TRUE;
    }
    return sprintf('%s="%s"', $name, $value);
  }
}