shop basket class

[capuozzo]

Hi to the community,

I am trying to build a shopping basket, then I ve found on the web a useful class

<?php
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU Library General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# Copyright (C) 2001 by Edward Rudd <[e-mail]>

define ('BASKET_ID','id');
define ('BASKET_NAME','name');
define ('BASKET_PRICE','price');
define ('BASKET_QUANTITY','quantity');
define ('BASKET_TAX','tax');
define ('BASKET_DATA','tax');

class Basket {
	var $basket_items;

    function Basket() {
	$this->basket_items=array();
    }
    function Add_Item($ID,$name,$quantity=1,$price=0,$tax=0,$data=NULL) {
	// find next item..
	$pos = $this->next_pos();
            $this->basket_items[$pos] = array(
	    BASKET_ID=>$ID,
	    BASKET_NAME=>$name,
	    BASKET_QUANTITY=>$quantity,
        	    BASKET_PRICE=>$price,
	    BASKET_TAX=>$tax,
        	    BASKET_DATA=>$data
	);
            return ($pos);
    }
    function Del_Item($pos) {
            $this->basket_items[$pos]=NULL;
    }


    function Get_Item_ID($pos) {
            return $this->basket_items[$pos][BASKET_ID];
    }
    function Get_Item_Name($pos) {
            return $this->basket_items[$pos][BASKET_NAME];
    }
    function Get_Item_Price($pos) {
            return $this->basket_items[$pos][BASKET_PRICE];
    }
    function Get_Item_Quantity($pos) {
            return $this->basket_items[$pos][BASKET_QUANTITY];
    }
    function Get_Item_Data($pos) {
            return $this->basket_items[$pos][BASKET_DATA];
    }
    function Set_Item_Quantity($pos,$quantity) {
            $this->basket_items[$pos][BASKET_QUANTITY]=$quantity;
    }
    function Inc_Item_Quantity($pos) {
            $this->basket_items[$pos][BASKET_QUANTITY]++;
    }
    function Set_Item_Data($pos,$data) {
            $this->basket_items[$pos][BASKET_QUANTITY]=$data;
    }

	function Enum_Items($start=false) {
            static $current;
	$total = count($this->basket_items);
            if (!$start && $current>=$total) return -1;
            if (!$start) {
                    $current++;
            } else {
                    $current=0;
            }
            while (($this->basket_items[$current]==NULL) && ($current<$total)) {
                    $current++;
            }
            return ($current<$total) ? $current : -1;
    }
    function Empty_Basket() {
            $this->basket_items=array();
    }
    function Get_Basket_Count() {
        $num=0;
        for ($i=0;$i<count($this->basket_items);$i++) {
			if ($this->basket_items[$i]!=NULL) $num++;
        }
        return $num;
    }
function Next_Pos() {
    for ($i=0;$i<count($this->basket_items);$i++) {
	if ($this->basket_items[$i]==NULL) {
	    return $i;
	}
    }
    return count($this->basket_items);
}
function Search_Item($ID) {
    if (empty($ID)) return -1;
    for ($i=0;$i<count($this->basket_items);$i++) {
	if ($this->basket_items[$i][BASKET_ID]==$ID) {
	    return $i;
	}
    }
    return -1;
}
}
?>

but the function Enum_Items return a value of -1 for the last element of the basket array.
Now it is a nice half day I look for the way to modify this function so that it could return a increment value for this holy last element , without arrive to do it.
With consequently headache.

Why I need to modify it?
Because the function Del_Item does not delete an item with a negative $pos

Do anybody help me?
Thank you.
Max (anymore : I had another nick here, but the forum is changed and I have lost my old password, the mail address I used and this is not a beautiful day for me. Wish better for you)