public static function explode($tags) {
    // This regexp allows the following types of user input:
    // this, "somecompany, llc", "and ""this"" w,o.rks", foo bar
    $regexp = '%(?:^|,\ *)("(?>[^"]*)(?>""[^"]* )*"|(?: [^",]*))%x';
    preg_match_all($regexp, $tags, $matches);
    $typed_tags = array_unique($matches[1]);

    $tags = array();
    foreach ($typed_tags as $tag) {
      // If a user has escaped a term (to demonstrate that it is a group,
      // or includes a comma or quote character), we remove the escape
      // formatting so to save the term into the database as the user intends.
      $tag = trim(str_replace('""', '"', preg_replace('/^"(.*)"$/', '\1', $tag)));
      if ($tag != "") {
        $tags[] = $tag;
      }
    }

    return $tags;
  }