Komma

if($fc_conn) {
  $i = 1;
  $str="";
  while($fc_data = dbarray($fc_result)) {
  $fc_user = dbarray(dbquery("SELECT user_name FROM ".DB_USERS." WHERE user_id=" . $fc_data['userid']));
 
  if ($i != $fc_conn) { $str .= "<font color=black><a href='".BASEDIR."profile.php?lookup=".$fc_data['userid']."' class='side'>".$fc_user['user_name']."</a>,\n</font>"; }

  else if ($fc_conn > ($fc_conn-1)) {
    $str = substr($str, 0, -1);   
    $str .= "<font color=black> og <a href='".BASEDIR."profile.php?lookup=".$fc_data['userid']."' class='side'>".$fc_user['user_name']."</a>\n</font>"; }

  else { $str .=  "<a href='".BASEDIR."profile.php?lookup=".$fc_data['userid']."' class='side'>".$fc_user['user_name']."</a> \n"; }

  $i++;
  }
  echo $str;
}

<?php
define('BASEDIR', '');

function get_users_from_database() {
    // dummy implementation - replace with real database code:
    return array(array('user_id' => 1, 'user_name' => 'Navn1'),
                array('user_id' => 2, 'user_name' => 'Navn2'),
                array('user_id' => 3, 'user_name' => 'Navn3'));
}

function build_user_url($user_id) {
    return BASEDIR . "profile.php?lookup=$user_id";   
}

function build_user_link($user_id, $user_name) {
    $url = build_user_url($user_id);
    return "<font color='black'><a href='$url'>$user_name</a></font>";
}

function human_language_implode($glue, $lastglue, $a) {
    if(count($a) == 0) {
        return '';
    } else if(count($a) == 1) {
        return $a[0];
    } else {
        return implode($glue, array_slice($a, 0, count($a) - 1)) . $lastglue . $a[count($a) - 1];
    }
   
}

function build_user_list($all_users) {
    $user_list_array = array_map(function($user) { return build_user_link($user['user_id'], $user['user_name']); }, $all_users);
    return human_language_implode(",\r\n", " og\r\n", $user_list_array);   
}

$all_users = get_users_from_database();
$user_list = build_user_list($all_users);
echo $user_list;
?>