I have problem with this code.. my browser prints:
Fatal error: Call to undefined function mysql_connect() in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\plaincart\library\database.php on line 4

ini_set('display_errors', 'On');

// start the session

// database connection config
$dbHost = 'localhost';
$dbUser = 'root';
$dbPass = '';
$dbName = 'plaincart';

// setting up the web root and server root for
// this shopping cart application
$thisFile = str_replace('\\', '/', __FILE__);

$webRoot  = str_replace(array($docRoot, 'library/config.php'), '', $thisFile);
$srvRoot  = str_replace('library/config.php', '', $thisFile);

define('WEB_ROOT', $webRoot);
define('SRV_ROOT', $srvRoot);

// these are the directories where we will store all
// category and product images
define('CATEGORY_IMAGE_DIR', 'images/category/');
define('PRODUCT_IMAGE_DIR',  'images/product/');

// some size limitation for the category
// and product images

// all category image width must not 
// exceed 75 pixels

// do we need to limit the product image width?
// setting this value to 'true' is recommended
define('LIMIT_PRODUCT_WIDTH',     true);

// maximum width for all product image

// the width for product thumbnail
define('THUMBNAIL_WIDTH',         75);

if (!get_magic_quotes_gpc()) {
	if (isset($_POST)) {
		foreach ($_POST as $key => $value) {
			$_POST[$key] =  trim(addslashes($value));
	if (isset($_GET)) {
		foreach ($_GET as $key => $value) {
			$_GET[$key] = trim(addslashes($value));

// since all page will require a database access
// and the common library is also used by all
// it's logical to load these library here
require_once 'database.php';
require_once 'common.php';

// get the shop configuration ( name, addres, etc ), all page need it
$shopConfig = getShopConfig();


require_once 'config.php';

$dbConn = mysql_connect ($dbHost, $dbUser, $dbPass) or die ('MySQL connect failed. ' . mysql_error());
mysql_select_db($dbName) or die('Cannot select database. ' . mysql_error());

function dbQuery($sql)
	$result = mysql_query($sql) or die(mysql_error());
	return $result;

function dbAffectedRows()
	global $dbConn;
	return mysql_affected_rows($dbConn);

function dbFetchArray($result, $resultType = MYSQL_NUM) {
	return mysql_fetch_array($result, $resultType);

function dbFetchAssoc($result)
	return mysql_fetch_assoc($result);

function dbFetchRow($result) 
	return mysql_fetch_row($result);

function dbFreeResult($result)
	return mysql_free_result($result);

function dbNumRows($result)
	return mysql_num_rows($result);

function dbSelect($dbName)
	return mysql_select_db($dbName);

function dbInsertId()
	return mysql_insert_id();

First: You need to include your code using code tags.

Second: In this case the code may not matter a lot. It may be the result of what you installed and how you have installed it. If you want to get PHP (and MySQL) working, the easiest way is use one of the packaged solution (see the list here).