Question

In PHP, I know there is no official way to delete items once they have been put into an array. But there must be a “best-method” solution to my problem. I believe this may lie in the array_filter function.

Essentially, I have a shopping cart object that stores items in a hashtable. Imagine you can only ever buy one of any item at a time.

I do

add_item(1);
add_item(2);
remove_item(1);

get_count() still returns 2.

var $items;


function add_item($id) {
    $this->items[$id] = new myitem($id);
}

function remove_item($id) {
    if ($this->items[$id]) {
        $this->items[$id] = false;
        return true;
    } else {    
        return false;
    }
}


function get_count() {
    return count($this->items);
}

What do people think is the best method to use in get_count? I can’t figure out the best way to use array_filter that simply doesn’t return false values (without writing a seperate callback).

Thanks 🙂

Answer 1

No official way? Sure there is! Unset!

<?php

class foo
{
    var $items = array();


    function add_item($id) {
            $this->items[$id] = new myitem($id);
    }

    function remove_item($id)
    {
        unset( $this->items[$id] );

    }


    function get_count() {
            return count($this->items);
    }
}

class myitem
{
    function myitem( $id )
    {
        // nothing
    }
}

$f = new foo();

$f->add_item( 1 );
$f->add_item( 2 );

$f->remove_item( 1 );

echo $f->get_count();

Also, is this PHP4? Because if not, you should look into some of the SPL stuff like ArrayObject or at least the the Countable and ArrayAccess interfaces.

EDIT

Here’s a version using the interfaces directly

<?php

class foo implements ArrayAccess, Countable
{
    protected $items = array();

    public function offsetExists( $offset )
    {
        return isset( $this->items );
    }

    public function offsetGet( $offset )
    {
        return $this->items[$offset];
    }

    public function offsetSet( $offset, $value )
    {
        $this->items[$offset] = $value;
    }

    public function offsetUnset( $offset )
    {
        unset( $this->items[$offset] );
    }

    public function count()
    {
        return count( $this->items );
    }

    public function addItem( $id )
    {
        $this[$id] = new myitem( $id );
    }
}

class myitem
{
    public function __construct( $id )
    {
        // nothing
    }
}

$f = new foo();

$f->addItem( 1 );
$f->addItem( 2 );
unset( $f[1] );

echo count( $f );

And here’s a version as an implementation of ArrayObject

<?php

class foo extends ArrayObject
{
    public function addItem( $id )
    {
        $this[$id] = new myitem( $id );
    }
}

class myitem
{
    public function __construct( $id )
    {
        // nothing
    }
}

$f = new foo();

$f->addItem( 1 );
$f->addItem( 2 );
unset( $f[1] );

echo count( $f );