# Class: Cart

A user can add a record to his shopping cart (we call it basket)
Because every user has his own basket, we store the information in a session variable, called cart
Because we need different actions (add item to cart, remove item from cart, clear the cart, ...) on different places ( shop detail, basket overview, ...), we'll make a new Cart class that handles all these actions
We can call these actions inside a view, inside a controller, inside a Livewire component, ...

# What are sessions?

A session can be defined as a server-side storage of information that is desired to persist throughout the user's interaction with the web site or web application

# How are sessions stored?

There are different ways to store a session
Most of the time, we use file based sessions but we can also use database based sessions or redis based sessions
Take a look at the session configuration file config/session.php
- The driver refers to the variable SESSION_DRIVER inside the .env file
- The lifetime refers to the variable SESSION_LIFETIME inside the .env file
- The expire_on_close is set to false, so the session is still active even if you close the browser

'driver' => env('SESSION_DRIVER', 'database'),
...
'lifetime' => env('SESSION_LIFETIME', 120),
'expire_on_close' => false,
 
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Now, take a look at the session variables inside .env:
- update the SESSION_DRIVER from database to file
- SESSION_LIFETIME is set to 120 minutes, or 2 hours

SESSION_DRIVER=file     #  replace database with file
SESSION_LIFETIME=120
 
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When you login to the site, you'll find one or more files with a random name inside the folder storage/framework/sessions
You can open a file to see what's inside a session

# Handle sessions

https://laravel.com/docs/9.x/session (opens new window)

Action	Laravel (helper)	Laravel (facade)	Pure PHP
set	`session()->put('key', 'val')`	`Session::put('key', 'val')`	`$_SESSION['key'] = 'val'`
get	`session()->get('key')`	`Session::get('key')`	`$_SESSION['key']`
remove key	`session()->forget('key')`	`Session::forget('key')`	`unset($_SESSION['key'])`
remove keys	`session()->forget(['key1', 'key2'])`	`Session::->forget(['key1', 'key2'])`
remove all keys	`session()->flush()`	`Session::flush()`	`session_destroy()`

# The Cart class

REMARK

In the next chapters, we'll use the Cart class to handle the shopping cart
To give you a better understanding what's going on, we'll explain the code by an example of what we want to achieve

Before we proceed to the Cart class itself, first take a look at the cart logic
Below you find an example of what's stored inside the session variable cart (in the next chapter, we'll actually get this result)
- 2 times the record with $id = 11 ( 2 * 16.49 € = 32.98 €)
- 1 time the record with $id = 15 ( 1 * 9.99 € = 9.99 €)
- Total items inside your basket = 3
- Total price for your basket = 32.98 € + 9.99 € = 42.97 €

Session cart

The cart is an associative array with three keys:
- the key records contains an associative array where the key represents the record id and the value contains (an associative array with) all the fields we need in the orderlines table
- The key totalQty contains the number of items in our cart
- The key totalPrice contains the total price of our cart

REMARKS

The Card is build upon a static class witch has the advantages of:
- no need to instantiate the class
- static properties and methods can be accessed directly with the scope resolution operator (_::_)
See static class example in /php/classes

# Create the Cart class

Create a new PHP Class (not a new file) Cart.php inside the folder app/Helpers
(In PhpStorm: right-click on the folder and choose New -> PHP Class)

# Initialize the $card property

Replace the content of the class with this code:
- Line 10 - 14he private static property $cart is an associative array with the three keys: records , totalQty and totalPrice
  Because this is a private property, we can only access it from inside the class
- Line 17 - 20: the public static method init() checks if the session variable cart exists
  - If the session variable cart exists, copy the session variable to the $cart variable
  - If not, use the default value of the $cart variable
- Line 32: call the init() method to make sure the $cart variable is initialized
  REMARK: this is the only place where we call the init() method, so we can be sure the $cart variable is initialized

<?php

namespace App\Helpers;

use App\Models\Record;
use Storage;

class Cart
{
    private static array $cart = [
        'records' => [],
        'totalQty' => 0,
        'totalPrice' => 0
    ];

    // initialize the cart
    public static function init(): void
    {
        self::$cart = session()->get('cart') ?? self::$cart;
    }
}

Cart::init();
 
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# Add/delete record to/from the cart and empty the cart

Line 18 - 32: check if this record is already in the cart
- If the record is already in the cart, increase the quantity of the record
- If not, add the record to the cart
  - Line 21 - 31: get the record from the database and add the id, artist, title, mb_id and the price and qty to the $cart variable
  - The quantity of the record is set to 1 (we just added the record to the cart)
  - If there is a cover image inside the public/storage/records folder, add the cover to the $cart variable, else use the default cover image
Line 33: call the updateTotal() method to update the total price and the total quantity
Line 41 and 42: start with $totalQty = 0 and $totalPrice = 0
Line 43 - 46: loop through the records array and add the qty and price to the $totalQty and $totalPrice variables
Line 47 and 48: update the $cart variable with the new $totalQty and $totalPrice variables
Line 49: store the $cart variable in the session variable cart

<?php

namespace App\Helpers;

use App\Models\Record;
use Storage;

class Cart
{
    private static array $cart = [ ... ];

    // initialize the cart
    public static function init(): void { ... }
    
    // add record to the cart
    public static function add(Record $record): void
    {
       $singlePrice = $record->price;
        if (array_key_exists($record->id, self::$cart['records'])) {
            self::$cart['records'][$record->id]['qty']++;
            self::$cart['records'][$record->id]['price'] += $singlePrice;
        } else {
            self::$cart['records'][$record->id] = [
                'id' => $record->id,
                'artist' => $record->artist,
                'title' => $record->title,
                'mb_id' => $record->mb_id,
                'cover' => Storage::disk('public')->exists('covers/' . $record->mb_id . '.jpg')
                    ? '/storage/covers/' . $record->mb_id . '.jpg'
                    : '/storage/covers/no-cover.png',
                'price' => $singlePrice,
                'qty' => 1
            ];
        }
        self::updateTotal();
    }
    
    // re-calculate the total quantity and price of records in the cart
    private static function updateTotal(): void
    {
        $totalQty = 0;
        $totalPrice = 0;
        foreach (self::$cart['records'] as $record) {
            $totalQty += $record['qty'];
            $totalPrice += $record['price'];
        }
        self::$cart['totalQty'] = $totalQty;
        self::$cart['totalPrice'] = $totalPrice;
        session()->put('cart', self::$cart);   // store the cart in the session
    }
}

Cart::init();
 
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Line 22 - 28: check if the record is in the cart
- If the record is in the cart, decrease the quantity of the record
- If not, do nothing
Line 25 - 27: if the quantity of the record is 0, remove the record from the cart
Line 29: call the updateTotal() method to update the total price and the total quantity

<?php

namespace App\Helpers;

use App\Models\Record;
use Storage;

class Cart
{
    private static array $cart = [ ... ];

    // initialize the cart
    public static function init(): void { ... }
    
    // add record to the cart
    public static function add(Record $record): void { ... }
    
    // delete record from the cart
    public static function delete(Record $record): void
    {
        $singlePrice = $record->price;
        if (array_key_exists($record->id, self::$cart['records'])) {
            self::$cart['records'][$record->id]['qty']--;
            self::$cart['records'][$record->id]['price'] -= $singlePrice;
            if (self::$cart['records'][$record->id]['qty'] == 0) {
                unset(self::$cart['records'][$record->id]);
            }
        }
        self::updateTotal();
    }
    
    // re-calculate the total quantity and price of records in the cart
    private static function updateTotal(): void { ... }
}

Cart::init();
 
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Line 24: remove the cart variable from the session
REMARK: there is no need to call the updateTotal() method, because the cart is empty

<?php

namespace App\Helpers;

use App\Models\Record;
use Storage;

class Cart
{
    private static array $cart = [ ... ];

    // initialize the cart
    public static function init(): void { ... }
    
    // add record to the cart
    public static function add(Record $record): void { ... }
    
    // delete record from the cart
    public static function delete(Record $record): void { ... }
    
    // empty the cart
    public static function empty(): void
    {
        session()->forget('cart');
    }
    
    // re-calculate the total quantity and price of records in the cart
    private static function updateTotal(): void { ... }
}

Cart::init();
 
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# Get data from the cart

With the six getters we can retrieve all the information or pieces of the information from the cart
- We provide all possible combinations here, even if we may not need them (yet)

<?php

namespace App\Helpers;

use App\Models\Record;
use Storage;

class Cart
{
    private static array $cart = [ ... ];

    // initialize the cart
    public static function init(): void { ... }
    
    // add record to the cart
    public static function add(Record $record): void { ... }
    
    // delete record from the cart
    public static function delete(Record $record): void { ... }
    
    // empty the cart
    public static function empty(): void { ... }
    
    // re-calculate the total quantity and price of records in the cart
    private static function updateTotal(): void { ... }
    
    // get the complete cart
    public static function getCart(): array
    {
        return self::$cart;
    } 
}

Cart::init();
 
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get complete card

<?php

namespace App\Helpers;

use App\Models\Record;
use Storage;

class Cart
{
    private static array $cart = [ ... ];

    // initialize the cart
    public static function init(): void { ... }
    
    // add record to the cart
    public static function add(Record $record): void { ... }
    
    // delete record from the cart
    public static function delete(Record $record): void { ... }
    
    // empty the cart
    public static function empty(): void { ... }
    
    // re-calculate the total quantity and price of records in the cart
    private static function updateTotal(): void { ... }
    
    // get the complete cart
    public static function getCart(): array { ... }
    
    // get all the records from the cart
    public static function getRecords(): array
    {
        return self::$cart['records'];
    }    
}

Cart::init();
 
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get all records

<?php

namespace App\Helpers;

use App\Models\Record;
use Storage;

class Cart
{
    private static array $cart = [ ... ];

    // initialize the cart
    public static function init(): void { ... }
    
    // add record to the cart
    public static function add(Record $record): void { ... }
    
    // delete record from the cart
    public static function delete(Record $record): void { ... }
    
    // empty the cart
    public static function empty(): void { ... }
    
    // re-calculate the total quantity and price of records in the cart
    private static function updateTotal(): void { ... }
    
    // get the complete cart
    public static function getCart(): array { ... }
    
    // get all the records from the cart
    public static function getRecords(): array { ... }
    
    // get one record from the cart
    public static function getOneRecord($key = 0): array
    {
        if (array_key_exists($key, self::$cart['records'])) {
            return self::$cart['records'][$key];
        }
        return [];
    }
}

Cart::init();
 
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get one records

<?php

namespace App\Helpers;

use App\Models\Record;
use Storage;

class Cart
{
    private static array $cart = [ ... ];

    // initialize the cart
    public static function init(): void { ... }
    
    // add record to the cart
    public static function add(Record $record): void { ... }
    
    // delete record from the cart
    public static function delete(Record $record): void { ... }
    
    // empty the cart
    public static function empty(): void { ... }
    
    // re-calculate the total quantity and price of records in the cart
    private static function updateTotal(): void { ... }
    
    // get the complete cart
    public static function getCart(): array { ... }
    
    // get all the records from the cart
    public static function getRecords(): array { ... }
    
    // get one record from the cart
    public static function getOneRecord($key = 0): array { ... }
    
    // get all the record keys
    public static function getKeys(): array
    {
        return array_keys(self::$cart['records']);
    }

    // get total quantity of records in the cart
    public static function getTotalQty(): int
    {
        return self::$cart['totalQty'];
    }

    // get total price of records in the cart
    public static function getTotalPrice(): float
    {
        return self::$cart['totalPrice'];
    }
}

Cart::init();
 
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get rest

# Add an alias for the Cart class

We can add an alias to the Cart class in the config/app.php file
- This way we can use the Cart class without the App\Helpers\ namespace
- We can also use the Cart class in the routes/web.php file without the namespace
Open the config/app.php file:
- Line 3: add the Card class to the aliases array at the bottom of the file

'aliases' => Facade::defaultAliases()->merge([
    // 'ExampleClass' => App\Example\ExampleClass::class,
    'Cart' => App\Helpers\Cart::class,
])->toArray(),
 
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