Change tr border based on longest element?

Here's the code:

                <?php
        mysqlLogin();
        $username = $_COOKIE['username'];
        $sql = mysql_query("SELECT username FROM `users` WHERE username!='$username'");
        if(mysql_num_rows($sql) != 0) {
       开发者_C百科     echo "<table class='usertable' align='center'>";
        } else {
            echo "<center>No users found!</center>";
        }
        while($row = mysql_fetch_array($sql)){
            $length = strlen($row['username']) . 'px';
            echo "<tr><td style='width: '$length'; border-bottom: 1px solid #000000'><center>" . $row['username'] . "</center></td></tr>";
        }
    ?>

I want to make the bottom-border the length of the longest username in the SQL database.

This makes no sense... a border directive in CSS has no length - it automatically assumes the length/height of the element it's a border of.

If you mean you want to indicate which particular cell has the longest username and highlight it with a border-bottom, then you'd need to know in advance which username is longest. You can't have PHP "recall" the HTML it's already output to add the border directive after the fact.