Q:

PHP: Make variables into SESSION?

I'm working in a assigment and I want to save the data into a SESSION so it can be modified by the user(as a primitive shopping cart), but I need some light in here.
A) The information comes from a POST form.
B) The output should look like this:
SHOPING LIST
1. Coffe 5 units, 6 USD.
2. Banana 3 units, 3 USD.
3. Etc (The list can be infinite)

C) This is my current code, as you can see there is no session. And I need the user to be able to add more items.
 <?php

//Variables
$item= $_POST['item'];
$quantity= $_POST['quantity'];
$code= $_POST['code'];

//List
$articulos = array(

  'Pinaple' => 1, 'Banana' => 2, 'Aple' => 3, 
  'Milk' => 1, 'Coffe' => 3, 'Butter' => 1,
  'Bread' => 2, 'Juice' => 1, 'Coconuts' => 1,
  'Yogurt' => 2, 'Beer' => 1, 'Wine' => 6,
  );

//Price
$price = $items[$item] * $quantity;

//Shoping List

echo  "<b>Shopping List</b></br>";

echo "1. ".$item." ".$quantity." units".", ".$price." USD.";

//Back to index
echo "</br> <a href='index.html'>Back to Index</a>";

?>

A:

$_SESSION["foo"] = "bar";

Also make sure you call session_start() before ANY output to the document. I can't stress this enough. I'm talking even before the DOCTYPE deceleration.
Then you should be able to from anywhere afterwards do..
echo $_SESSION["foo"]; // output: bar
$_SESSION["foo"] = "new bar";
$_SESSION["new foo"] = $_SESSION["foo"];

and
$_SESSION["items"] = array("pants", "hat");
array_push($_SESSION["items"], "shirt");

etc.

