如果字符串中不存在，则添加另一个用户ID

I'm using this function;

function add_profile_visitor($add_uid,$to_uid,$visitors_list)
{
    global $db;
        $list = trim($visitors_list);
        $list_users = explode(",",$list);

        if (in_array($add_uid,$list_users))
        {
            return;
        }
        else
        {
            if (strpos($list_users,",") || strlen($list_users) > 0)
            {
                $newlist = $list_users.",".intval($add_uid);
            }
            else
            {
                $newlist = intval($add_uid);
            }
            $db->query("UPDATE users SET profile_visitor='".$db->escape_string($newlist)."' WHERE uid=".$to_uid);
        }

}

I want to add a User ID if its not present already in the field profile_visitor. For your notice, the profile_visitor list is comma separated list. Here are the variable's legend:

$add_uid = The user id that is going to be inserted in profile_visitor if its not present in already. $to_uid = The User ID where profile_visitor column is present and the $add_uid add in if its not present. $visitors_list = The comma separated list of profile visitors. Before adding any User ID that list will be empty (obviously)

The issue is: Each time the page loads (where that function is running) the list profile_visitor has the new User ID instead of adding the new User ID to the list.

Please help

Change your function to this:

function add_profile_visitor($add_uid,$to_uid,$visitors_list)
{
    global $db;
        $list = trim($visitors_list);
        $list_users = explode(",",$list);

        if (in_array($add_uid,$list_users))
        {
            return;
        }
        else
        {
            if (strpos($list,",") || strlen($list) > 0)
            {
                $newlist = $list.",".intval($add_uid);
            }
            else
            {
                $newlist = intval($add_uid);
            }
            $db->query("UPDATE users SET profile_visitor='".$db->escape_string($newlist)."' WHERE uid=".$to_uid);
        }

}