Question

function formatUpdate($tweet,$dt,$picture,$username)
{
    if(is_string($dt)) $dt=strtotime($dt);

    $tweet=htmlspecialchars(stripslashes($tweet));


       $at = "@" . $username;




    return'
    <li>
    <a href="nano.com/' . $username . '"><img class="avatar" src="images/' . $picture . '" width="48" height="48" alt="avatar" /></a>
    <div class="tweetTxt">
    <strong><a href="nano.com/' . $username . '">' . $username . '</a></strong> '. preg_replace('/((?:http|https|ftp):\/\/(?:[A-Z0-9][A-Z0-9_-]*(?:\.[A-Z0-9][A-Z0-9_-]*)+):?(\d+)?\/?[^\s\"\']+)/i','<a href="$1" rel="nofollow" target="blank">$1</a>',$tweet).'
    <div class="date">'.relativeTime($dt).'</div> <a class ="reply"  href="?replyto=' echo $at;   '">reply</a>
    </div>
    <div class="clear"></div>
    </li>';

}

Answer 1

To append the value of a variable to a string you need not echo the variable.

You have

href="?replyto=' echo $at;   '">reply</a>

Change it to

href="?replyto='. $at .'">reply</a>