摆脱最后一个逗号[重复]

Possible Duplicate:
Removing last comma in PHP?
Remove the last Comma from a string (PHP / Wordpress)

I have code which from some reason is not working. What I am trying to do is get rid of last comma from the result but it won't work. Here is the code

 <?php do { 
  $activity_user_first_name = $row_product_activity['user_first_name'];
  $activity_user_last_name = $row_product_activity['user_last_name'];
  $name = '<a href="">'.$activity_user_first_name.' '.$activity_user_last_name.'</a>, ';
  echo rtrim($name, ",");
 } while($row_product_activity = mysql_fetch_assoc($product_activity)) ?> like this

So the results I want to get is this

Steve Jobs, Bill Gates, Sergey Brin, Larry Page like this

instead I get this

Steve Jobs, Bill Gates, Sergey Brin, Larry Page, like this

so I want that comma after Larry Page or any other name that is at the end be deleted. I tried playing around with many other options but the nothing came up as I wish. Any suggestions would be appreciated.

I think a better solution is to construct the string without the trailing comma in the first place. Put the links for each name into an array slot and then just echo some imploded results.

<?php 
    $names=array();
    do { 
        $activity_user_first_name = $row_product_activity['user_first_name'];
        $activity_user_last_name = $row_product_activity['user_last_name'];
        $names[] = '<a href="#">'.$activity_user_first_name.' '.$activity_user_last_name.'</a>';
    } while($row_product_activity = mysql_fetch_assoc($product_activity));

    echo implode(', ', $names);    

?> Like This