Converting username text to url

[DJ29Joesph]

I created a function I was wondering if I could have someone look it over. It pretty much takes the text in a post and looks for a username, and if there is one, it will mark it up as url and usergroup color. Anyway heres the code.

PHP Code:

function convert_username_to_url($text1)
{
    global $vbulletin;

    if ($vbulletin->$bbuserinfo[userid] > 0)
    {
        $userSearchQuery = $vbulletin->db->query_read("
        SELECT userid, usergroupid, displaygroupid, username
        FROM' . TABLE_PREFIX . 'user
        ");
        
        While ($customuser = $vbulletin->db->fetch_array($userSearchQuery))
        {
            fetch_musername($customuser);
            $userSearch = array($customuser[username]);
            $userReplace =     '<a href="member.php?' . $vbulletin->session->vars['sessionurl'] . "u=$customuser[userid]\">$customuser[musername]</a>";
        }
        
    }
    $text = str_replace($userSearch, $userReplace, $text1);
                    
    return $text;
} 


Again if you could take a look that would be awesome. I know html, I'm trying to learn php. Thanks