I want my auction site changed so that when you click the "place bid" button it will work like this
if bid >= reserve price the auction ends with the bid = selling price
else message "bid too low" current bid = 0 (again)
This should take only 2 or 3 lines of code but I cant work it out.
here is some of the code as it all won't fit.

include 'includes/common.inc.php';
include $include_path . 'datacheck.inc.php';

$NOW = time();
$id = intval($_REQUEST['id']);
$bid = $_POST['bid'];
$qty = (isset($_POST['qty'])) ? intval($_POST['qty']) : 1;
$bidder_id = $user->user_data['id'];
$bidding_ended = false;

if (!$user->is_logged_in())
{
    $_SESSION['REDIRECT_AFTER_LOGIN'] = 'bid.php?id=' . $id;
    header('location: user_login.php');
    exit;
}

if (in_array($user->user_data['suspended'], array(5, 6, 7)))
{
    header('location: message.php');
    exit;
}

if (!$user->can_buy)
{
    $_SESSION['TMP_MSG'] = $MSG['819'];
    header('location: user_menu.php');
    exit;
}

if ($system->SETTINGS['usersauth'] == 'y' && $system->SETTINGS['https'] == 'y' && $_SERVER['HTTPS'] != 'on')
{
    $sslurl = str_replace('http://', 'https://', $system->SETTINGS['siteurl']);
    $sslurl = (!empty($system->SETTINGS['https_url'])) ? $system->SETTINGS['https_url'] : $sslurl;
    header('location: ' . $sslurl . 'bid.php?id=' . $id . '&bid=' . $bid . '&qty=' . $qty);
    exit;
}

function get_increment($val, $input_check = true)
{
    global $system, $DBPrefix;

    if ($input_check)
        $val = $system->input_money($val);
    $query = "SELECT increment FROM " . $DBPrefix . "increments 
            WHERE ((low <= " . $val . " AND high >= " . $val . ")
            OR (low < " . $val . " AND high < " . $val . ")) ORDER BY increment DESC";
    $res = mysql_query($query);
    $system->check_mysql($res, $query, __LINE__, __FILE__);
    $increment = mysql_result($res, 0, 'increment');
    return $increment;
}

function extend_auction($id, $ends)
{
    global $system, $DBPrefix;

    if ($system->SETTINGS['ae_status'] == 'enabled' && ($ends - $system->SETTINGS['ae_timebefore']) < time())
    {
        $query = "UPDATE " . $DBPrefix . "auctions SET ends = ends + " . $system->SETTINGS['ae_extend'] . " WHERE id = " . $id;
        $res = mysql_query($query);
        $system->check_mysql($res, $query, __LINE__, __FILE__);
    }
}

// first check if valid auction ID passed
$query = "SELECT a.*, u.nick, u.email, u.id AS uId FROM " . $DBPrefix . "auctions a
        LEFT JOIN " . $DBPrefix . "users u ON (a.user = u.id)
        WHERE a.id = " . $id;
$res = mysql_query($query);
$system->check_mysql($res, $query, __LINE__, __FILE__);
// such auction does not exist
if (mysql_num_rows($res) == 0)
{
    $template->assign_vars(array(
            'TITLE_MESSAGE' => $MSG['415'],
            'BODY_MESSAGE' => $ERR_606
            ));
    include 'header.php';
    $template->set_filenames(array(
            'body' => 'message.tpl'
            ));
    $template->display('body');
    include 'footer.php';
    exit; // kill the page
}

// check user entered a bid
if (empty($bid) && !isset($errmsg))
{
    $errmsg = $ERR_072;
}

// check the bid is valid
if (!$system->CheckMoney($bid) && !isset($errmsg))
{
    $errmsg = $ERR_058;
}

// reformat bid to valid number
$bid = $system->input_money($bid);

$Data = mysql_fetch_array($res);
$item_title = $Data['title'];
$item_id = $Data['id'];
$seller_name = $Data['nick']; 
$seller_email = $Data['email'];
$atype = $Data['auction_type'];
$aquantity = $Data['quantity'];
$minimum_bid = $Data['minimum_bid'];
$customincrement = $Data['increment'];
$current_bid = $Data['current_bid'];
$pict_url_plain = $Data['pict_url'];
$reserve = $Data['reserve_price'];
$c = $Data['ends'];
$cbid = ($current_bid == 0) ? $minimum_bid : $current_bid;

if (($Data['ends'] <= time() || $Data['closed'] == 1) && !isset($errmsg))
{
    $errmsg = $ERR_614;
}
if (($Data['starts'] > time()) && !isset($errmsg))
{
    $errmsg = $ERR_073;
}
if ($aquantity < $qty)
{
    $errmsg = $ERR_608;
}

$query = "SELECT bid, bidder FROM " . $DBPrefix . "bids WHERE auction = " . $id . " ORDER BY bid DESC, id DESC LIMIT 1";
$res = mysql_query($query);
$system->check_mysql($res, $query, __LINE__, __FILE__);
if (mysql_num_rows($res) > 0)
{
    $high_bid = mysql_result($res, 0, 'bid');
    $WINNING_BIDDER = mysql_result($res, 0, 'bidder');
    $ARETHEREBIDS = ' | <a href="' . $system->SETTINGS['siteurl'] . 'item.php?id=' . $id . '&history=view#history">' . $MSG['105'] . '</a>';
}
else
{
    $high_bid = $current_bid;
}

if ($customincrement > 0)
{
    $increment = $customincrement;
}
else
{
    $increment = get_increment($high_bid, false);
}

if (ceil($high_bid) == 0 || $atype == 2)
{
    $next_bid = $minimum_bid;
}
else
{
    $next_bid = $high_bid + $increment;
}

$tmpmsg = CheckBidData();
if ($tmpmsg != 0 && !isset($errmsg))
{
    $errmsg = ${'ERR_' . $tmpmsg};
}

if (isset($_POST['action']) && !isset($errmsg))
{
    if ($system->SETTINGS['usersauth'] == 'y')
    {
        if (strlen($_POST['password']) == 0)
        {
            $errmsg = $ERR_004;
        }
        $query = "SELECT * FROM " . $DBPrefix . "users WHERE id = " . $user->user_data['id'] . " AND password = '" . md5($MD5_PREFIX . $_POST['password']) . "'";
        $res = mysql_query($query);
        $system->check_mysql($res, $query, __LINE__, __FILE__);
        if (mysql_num_rows($res) == 0)
        {
            $errmsg = $ERR_611;
        }
    }
    $send_email = false;
    // make the bid
    if ($atype == 1 && !isset($errmsg)) // normal auction
    {
        if ($system->SETTINGS['proxy_bidding'] == 'n')
        {
            // is it the highest bid?
            if ($current_bid < $bid)
            {
                // did you outbid someone?
                $query = "SELECT u.id FROM " . $DBPrefix . "bids b, " . $DBPrefix . "users u WHERE b.auction = " . $id . " AND b.bidder = u.id and u.suspended = 0 ORDER BY bid DESC";
                $result = mysql_query($query);
                $system->check_mysql($result, $query, __LINE__, __FILE__);
                if (mysql_num_rows($res) == 0 || mysql_result($res, 0) != $bidder_id)
                {
                    $send_email = true;
                }
                $query = "UPDATE " . $DBPrefix . "auctions SET current_bid = " . $bid . ", num_bids = num_bids + 1 WHERE id = " . $id;
                $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                // Also update bids table
                $query = "INSERT INTO " . $DBPrefix . "bids VALUES (NULL, " . $id . ", " . $bidder_id . ", " . $bid . ", '" . $NOW . "', " . $qty . ")";
                $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                extend_auction($item_id, $c);
                $bidding_ended = true;
            }
        }
        elseif ($WINNING_BIDDER == $bidder_id)
        {
            $query = "SELECT bid FROM " . $DBPrefix . "proxybid p
                    LEFT JOIN " . $DBPrefix . "users u ON (p.userid = u.id)
                    WHERE userid = " . $user->user_data['id'] . " AND itemid = " . $id . " ORDER BY bid DESC";
            $res = mysql_query($query);
            $system->check_mysql($res, $query, __LINE__, __FILE__);
            if (mysql_num_rows($res) > 0)
            {
                $WINNER_PROXYBID = mysql_result($res, 0, 'bid');
                if ($WINNER_PROXYBID >= $bid)
                {
                    $errmsg = $ERR_040;
                }
                else
                {
                    // Just update proxy_bid
                    $query = "UPDATE " . $DBPrefix . "proxybid SET bid = " . floatval($bid) . "
                              WHERE userid = " . $user->user_data['id'] . "
                              AND itemid = " . $id . " AND bid = " . $WINNER_PROXYBID;
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);

                    if ($reserve > 0 && $reserve > $current_bid && $bid >= $reserve)
                    {
                        $query = "UPDATE " . $DBPrefix . "auctions SET current_bid = " . floatval($reserve) . ", num_bids = num_bids + 1 WHERE id = " . $id;
                        $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                        // Also update bids table
                        $query = "INSERT INTO " . $DBPrefix . "bids VALUES (NULL, " . $id . ", " . $bidder_id . ", " . floatval($reserve) . ", '" . $NOW . "', " . $qty . ")";
                        $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                    }
                    extend_auction($item_id, $c);
                    $bidding_ended = true;
                }
            }
        }
        if (!$bidding_ended && !isset($errmsg) && $system->SETTINGS['proxy_bidding'] == 'y')
        {
            $query = "SELECT * FROM " . $DBPrefix . "proxybid p, " . $DBPrefix . "users u WHERE itemid = " . $id . " AND p.userid = u.id and u.suspended = 0 ORDER by bid DESC";
            $result = mysql_query($query);
            $system->check_mysql($result, $query, __LINE__, __FILE__);
            if (mysql_num_rows($result) == 0) // First bid
            {
                if ($next_bid < $bid)
                {
                    $query = "INSERT INTO " . $DBPrefix . "proxybid VALUES (" . intval($id) . "," . intval($bidder_id) . "," . floatval($bid) . ")";
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                }

                if ($reserve > 0 && $reserve > $current_bid && $bid >= $reserve)
                {
                    $next_bid = $reserve;
                }
                // Only updates current bid if it is a new bidder, not the current one
                $query = "UPDATE " . $DBPrefix . "auctions SET current_bid = $next_bid, num_bids = num_bids + 1 WHERE id = " . $id;
                $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                // Also update bids table
                $query = "INSERT INTO " . $DBPrefix . "bids VALUES (NULL, " . $id . ", " . $bidder_id . ", " . floatval($next_bid) . ", '" . $NOW . "', " . $qty . ")";
                $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                $query = "UPDATE " . $DBPrefix . "counters SET bids = (bids + 1)";
                $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
            }
            else // This is not the first bid
            {
                $proxy_bidder_id = mysql_result($result, 0, 'userid');
                $proxy_max_bid = mysql_result($result, 0, 'bid');

                if ($proxy_max_bid < $bid)
                {
                    if ($proxy_bidder_id != $bidder_id)
                    {
                        $send_email = true;
                    }
                    $next_bid = $proxy_max_bid + $increment;
                    if (($proxy_max_bid + $increment) > $bid)
                    {
                        $next_bid = $bid;
                    }

                    $query = "INSERT INTO " . $DBPrefix . "proxybid VALUES (" . $id . ", " . $bidder_id . ", " . floatval($bid) . ")";
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);

                    if ($reserve > 0 && $reserve > $current_bid && $bid >= $reserve)
                    {
                        $next_bid = $reserve;
                    }
                    // Fake bid to maintain a coherent history
                    if ($current_bid < $proxy_max_bid)
                    {
                        $query = "INSERT INTO " . $DBPrefix . "bids VALUES (NULL, " . $id . "," . $proxy_bidder_id . "," . floatval($proxy_max_bid) . ",'" . $NOW . "'," . $qty . ")";
                        $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                        $fakebids = 1;
                    }
                    else
                    {
                        $fakebids = 0;
                    }

Here is the rest of the code

                    // Update bids table
                    $query = "INSERT INTO " . $DBPrefix . "bids VALUES (NULL, " . $id . ", " . $bidder_id . ", " . floatval($next_bid) . ", '" . $NOW . "', " . $qty . ")";
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                    $query = "UPDATE " . $DBPrefix . "counters SET bids = (bids + (1 + " . $fakebids . "))";
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                    $query = "UPDATE " . $DBPrefix . "auctions SET current_bid = " . $next_bid . ", num_bids = (num_bids + 1 + " . $fakebids . ") WHERE id = " . $id;
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                }
                if ($proxy_max_bid == $bid)
                {
                    $cbid = $proxy_max_bid;
                    $errmsg = $MSG['701'];
                    // Update bids table
                    $query = "INSERT INTO " . $DBPrefix . "bids VALUES (NULL, " . $id . ", " . $bidder_id . ", " . floatval($bid) . ", '" . $NOW . "', " . $qty . ")";
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                    $query = "INSERT INTO " . $DBPrefix . "bids VALUES (NULL, " . $id . ", " . $proxy_bidder_id . ", " . floatval($cbid) . ", '" . $NOW . "', " . $qty . ")";
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                    $query = "UPDATE " . $DBPrefix . "counters SET bids = (bids + 2)";
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                    $query = "UPDATE " . $DBPrefix . "auctions SET current_bid = " . floatval($cbid) . ", num_bids = num_bids + 1 WHERE id = " . $id;
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                    if ($customincrement == 0)
                    {
                        // get new increment
                        $increment = get_increment($cbid);
                    }
                    else
                    {
                        $increment = $customincrement;
                    }
                    $next_bid = $cbid + $increment;
                }
                if ($proxy_max_bid > $bid)
                {
                    // Update bids table
                    $query = "INSERT INTO " . $DBPrefix . "bids VALUES (NULL, " . $id . ", " . $bidder_id . ", " . floatval($bid) . ", '" . $NOW . "', " . $qty . ")";
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                    if ($customincrement == 0)
                    {
                        // get new increment
                        $increment = get_increment($bid);
                    }
                    else
                    {
                        $increment = $customincrement;
                    }
                    if ($bid + $increment - $proxy_max_bid >= 0)
                    {
                        $cbid = $proxy_max_bid;
                    }
                    else
                    {
                        $cbid = $bid + $increment;
                    }
                    $errmsg = $MSG['701'];
                    // Update bids table
                    $query = "INSERT INTO " . $DBPrefix . "bids VALUES (NULL, " . $id . ", " . $proxy_bidder_id . ", " . floatval($cbid) . ", '" . $NOW . "', " . $qty . ")";
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                    $query = "UPDATE " . $DBPrefix . "counters SET bids = (bids + 2)";
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                    $query = "UPDATE " . $DBPrefix . "auctions SET current_bid = " . floatval($cbid) . ", num_bids = num_bids + 1 WHERE id = " . $id;
                    $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
                    if ($customincrement == 0)
                    {
                        // get new increment
                        $increment = get_increment($cbid);
                    }
                    else
                    {
                        $increment = $customincrement;
                    }
                    $next_bid = $cbid + $increment;
                }
            }
            extend_auction($item_id, $c);
        }
    }
    elseif ($atype == 2 && !isset($errmsg)) // dutch auction
    {
        // If the bidder already bid on this auction there new bbid must be higher
        $query = "SELECT bid, quantity FROM " . $DBPrefix . "bids WHERE bidder = " . $bidder_id . " AND auction = " . $id . " ORDER BY bid DESC LIMIT 1";
        $res = mysql_query($query);
        $system->check_mysql($res, $query, __LINE__, __FILE__);
        if (mysql_num_rows($res) > 0)
        {
            $PREVIOUSBID = mysql_fetch_array($res);
            if (($bid * $qty) <= ($PREVIOUSBID['bid'] * $PREVIOUSBID['quantity']))
            {
                $errmsg = $ERR_059;
            }
        }
        if (!isset($errmsg))
        {
            $query = "INSERT INTO " . $DBPrefix . "bids VALUES (NULL, " . $id . ", " . $bidder_id . ", " . floatval($bid) . ", '" . $NOW . "', " . $qty . ")";
            $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
            $query = "UPDATE " . $DBPrefix . "counters SET bids = (bids + 1)";
            $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
            $query = "UPDATE " . $DBPrefix . "auctions SET current_bid = " . floatval($bid) . ", num_bids = num_bids + 1 WHERE id = " . $id;
            $system->check_mysql(mysql_query($query), $query, __LINE__, __FILE__);
        }
    }
    // send emails where needed
    $query = "SELECT bidder, bid FROM " . $DBPrefix . "bids WHERE auction = " . $id . " ORDER BY bid DESC";
    $result = mysql_query($query);
    $system->check_mysql($result, $query, __LINE__, __FILE__);

    if (mysql_num_rows($result) > 1)
    {
        $OldWinner_id = mysql_result($result, 1, 'bidder');
        $new_bid = $next_bid;
        $OldWinner_bid = $system->print_money($new_bid - $increment);

        $query = "SELECT * FROM " . $DBPrefix . "users WHERE id = " . $OldWinner_id;
        $result_old_winner = mysql_query($query);
        $system->check_mysql($result_old_winner, $query, __LINE__, __FILE__);

        $OldWinner_nick = mysql_result($result_old_winner, 0, 'nick');
        $OldWinner_name = mysql_result($result_old_winner, 0, 'name');
        $OldWinner_email = mysql_result($result_old_winner, 0, 'email');
    }
    // Update counters table with the new bid
    // Send notification if users keyword matches (Item Watch)
    $query = "SELECT id, email, name, item_watch FROM " . $DBPrefix . "users WHERE item_watch != '' AND  item_watch != NULL AND id != " . $bidder_id;
    $result = mysql_query($query);
    $system->check_mysql($result, $query, __LINE__, __FILE__);

    while ($row = mysql_fetch_assoc($result))
    {
        // If keyword matches with opened auction title or/and desc send user a mail
        if (strstr($row['item_watch'], $id) !== false)
        {
            // Get data about the auction
            $query = "SELECT title, current_bid FROM " . $DBPrefix . "auctions WHERE id = " . intval($id);
            $res = mysql_query($query);
            $system->check_mysql($res, $query, __LINE__, __FILE__);
            $emailer = new email_class();
            $emailer->assign_vars(array(
                    'REALNAME' => $row['name'],
                    'TITLE' => mysql_result($res, 0, 'title'),
                    'BID' => $system->print_money(mysql_result($res, 0, 'current_bid'), false),
                    'AUCTION_URL' => $system->SETTINGS['siteurl'] . 'item.php?id=' . $id
                    ));
            $emailer->email_uid = $row['id'];
            $emailer->email_sender($row['email'], 'item_watch.inc.php', $system->SETTINGS['sitename'] . ' - ' . $MSG['472']);
        }
    }
    // End of Item watch
    if ($send_email)
    {
        $month = gmdate('m', $c + $system->tdiff);
        $ends_string = $MSG['MON_0' . $month] . ' ' . gmdate('d, Y H:i', $c + $system->tdiff);
        $new_bid = $system->print_money($next_bid);
        // Send e-mail message
        include $include_path . 'no_longer_winner.inc.php';
    }
    $template->assign_vars(array(
            'PAGE' => 2,
            'BID_HISTORY' => (isset($ARETHEREBIDS)) ? $ARETHEREBIDS : '',
            'ID' => $id,
            'BID' => $system->print_money($bid)
            ));
}
if (!isset($_POST['action']) || isset($errmsg))
{
    // just set the needed template variables
    $template->assign_vars(array(
            'PAGE' => 1,
            'ERROR' => (isset($errmsg)) ? $errmsg : '',
            'BID_HISTORY' => (isset($ARETHEREBIDS)) ? $ARETHEREBIDS : '',
            'ID' => $id,
            'IMAGE' => (!empty($pict_url_plain)) ? '<img src="getthumb.php?w=' . $system->SETTINGS['thumb_show'] . '&fromfile=' . $uploaded_path . $id . '/' . $pict_url_plain . '" border="0" align="center">' : '&nbsp;',
            'TITLE' => $item_title,
            'CURRENT_BID' => $system->print_money($cbid),
            'ATYPE' => $atype,
            'BID' => $system->print_money_nosymbol($bid),
            'NEXT_BID' => $system->print_money($next_bid),
            'QTY' => $qty,
            'TQTY' => $aquantity,
            'AGREEMENT' => sprintf($MSG['25_0086'], $system->print_money($qty * $bid)),
            'CURRENCY' => $system->SETTINGS['currency'],

            'B_USERAUTH' => ($system->SETTINGS['usersauth'] == 'y')
            ));
}

include 'header.php';
$template->set_filenames(array(
        'body' => 'bid.tpl'
        ));
$template->display('body');
include 'footer.php';
?>
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