The section on extended functionality covers non-GUI classes that provide often needed application functions without a user interface. Some extended classes depend on core functionality, some contain independent classes.
Extended classes are treated differently from core classes in
that their code is not automatically included by
prepend.php3
. You have to include the class definition
manually where needed or you modify prepend.php3
.
The Cart class is programmatically independent, but makes sense
only if its instances are made persistent in some way. The Cart
class automatically registers itself as a session variable in
its start()
function.
Cart implements a shopping cart. At the moment, items within the shopping cart are independent of each other; the cart can only hold simple things. Support for compound articles that require other articles to function and provide a base for dependent articles is to be added at a future time.
An example of a simple article is any article with no options, for example an apple or a book. Common examples for compound articles are a pizza (which requires a foundation in either American or Italian style, a selection of toppings, and cheese, to function correctly) and a computer system (which requires a housing, a motherboard, RAM, a video card, etc to function correctly).
Note: Cart
was a core class up to release-5. If
your applications uses the Cart
class, you must
manually add the statement include("cart.inc")
to your
prepend.php3
file where indicated in that file.
Note: The page management functions do no longer support
the feature cart
to set up and start the cart class. It is
recommended that you use Session
's auto_init
feature
instead to start your cart automatically or that you manually
set up your cart.
classname | Serialization helper: The name of this class. |
persistent_slots | Serialization helper: The names of all persistent slots. |
item | Multidimensional array of items in the cart. |
currentItem | A counter for item positions. |
|
Checks that an item with the given article number $art
is
in the cart. Returns an array of a boolean value and an integer
number. If the boolean is true, there are number many articles
of that article number in the cart.
Add $num
many articles of article number $art
to the current
shopping cart. Returns the position number of $art
in the
shopping cart.
Remove $num
many articles of article number $art
from the
shopping cart, if there are at least that many articles in the
cart. Returns the position number of $art
in the shopping cart
or false, if there weren't enough $art
to remove them from the
cart. If the function does return false, the cart has not been
modified.
Calls show_item_open()
once at the beginning of a shopping
cart listing. Then calls show_item()
once for each item in
the shopping cart. Calls show_item_close()
once at the end
of a shopping cart listing.
This function should be provided by the user. It renders the
HTML to display a single item from the cart. $art
is the
article number of the item and there are $num
of these in
the cart.
This function should be provided by the user. It renders the prologue HTML to display a shopping cart listing.
This function should be provided by the user. It renders the epilogue HTML to display a shopping cart listing.
Use a subclass of Cart
to provide an implementation of
show_item()
.
class My_Cart extends Cart {
var $classname = "My_Cart";
// Look up article numbers...
var $database_class = "DB_Article";
var $database_table = "articles";
var $db;
var $sum = 0;
function show_cart_open() {
printf("<table class=cart_table>\n");
$this->sum = 0;
}
function show_cart_close() {
printf("</table>\n");
printf("That's a total of %s.\n", $this->sum);
}
function show_item($art, $num) {
if (!is_object($this->db)) {
$class = $this->database_class;
$this->db = new $class;
}
$query = sprintf("select * from %s where artid = '%s'",
$this->database-table,
$art);
$this->db->query($query);
while($this->db->next_record()) {
printf(" <tr class=cart_row>\n <td class=cart_cell>%s</td>\n",
$this->db->Record["name"]);
printf(" <td class=cart_cell>%s</td>\n",
$this->db->Record["price"]);
printf(" <td class=cart_cell>%s</td>\n",
$num);
$rowsum = $num * $this->db->Record["price"];
$this->sum += $rowsum;
printf(" <td class=cart_cell>%s</td>\n",
$rowsum);
printf(" </tr>\n");
}
}
}
To use a cart, create an instance of your Cart
subclass and
call start()
. This will automatically register cart
.
It is recommended that you set in your Session
subclass
in local.inc
the slot $auto_init
to the value
setup.inc
and create an include file of that name which
contains the following code:
global $cart; ## $cart is a global variable.
$cart = new My_Cart; ## Make a My_Cart instance named $cart
$cart->start(); ## and have it register itself.
Use add_item()
and remove_item
to work with your Cart:
$cart->add_item("101", 2); ## Add two pieces of "101"
$cart->remove_item("101", 1); ## Drop one piece of "101"
Use show_all()
to display the contents of your cart.
$cart->show_all(); ## What's in a cart, anyway?