M2 | How to create global variable that can be used only in the same class?

Question

The scenario is I have multiple if-conditions to create product programmatically or load at controller action. I need a single variable who's value should be updating through different functions.

I have tried custom php ways but are not working. How can I achieve this?

Edit

Here is my class, I want to create product one(first) time and after that each time same product should gets load so that it could be added to cart programmatically. I am loading product using SKU. To read code please focus on $sku variable which I want to make global or static.

class Index extends \Magento\Framework\App\Action\Action
{
protected $resultPageFactory;
protected $session;
protected $sku;
private $productRepository;
public function __construct(
    FormKey $formKey,
    Cart $cart,
    Product $product,
    \Magento\Framework\App\Action\Context $context,
    \Magento\Customer\Model\Session $customerSession,
    \Magento\Catalog\Api\ProductRepositoryInterface $productRepository,
    PageFactory $resultPageFactory
)
{
    $this->session = $customerSession;
    $this->formKey = $formKey;
    $this->sku = $sku;
    $this->cart = $cart;
    $this->productRepository = $productRepository;
    $this->product = $product; 
    parent::__construct($context);
    $this->resultPageFactory = $resultPageFactory;
}
public function execute()
{
    if (!$this->session->isLoggedIn())
    {
        $resultRedirect = $this->resultRedirectFactory->create();
        $resultRedirect->setPath('customer/account/login');
        return $resultRedirect;
    }
    else
    {
        $resultPage = $this->resultPageFactory->create();
        $resultPage->getConfig()->getTitle()->set(__('My Wallet'));


        $vat_exempt_name = $this->getRequest()->getPost('vat_exempt_name');
         //...........Load Product...............//
        $product= $this->loadMyProduct();
        $ID = $product->getId();

    //.............. For Add to Cart .........//
    $productId =$ID;
    $params = array(
                'form_key' => $this->formKey->getFormKey(),
                'product' => $productId, 
                'qty'   =>1
            );
        $product = $this->product->load($productId);       
        $this->cart->addProduct($product, $params);
        $this->cart->save();
        return $resultPage;
    }
} 
    public function loadMyProduct()
    {   
        if (empty($this->sku)){
        $this->createProduct();
        }
        else{
        return $this->productRepository->get($this->sku);
        }
    }
    public function createProduct(){
        $posted = $this->getRequest()->getParam('vat_exempt_name');
        $objectManager = \Magento\Framework\App\ObjectManager::getInstance(); // instance of object manager
        $product = $objectManager->create('\Magento\Catalog\Model\Product');
        $product->setSku('my-sku44'); // I need this SKU to be set for global variable $sku
        $product->setName('Wallet Amount'); // Name of Product
        $product->setAttributeSetId(4); // Attribute set id
        $product->setStatus(1); // Status on product enabled/ disabled 1/0
        $product->setWebsiteIds(array(1));
        $product->setWeight(10); // weight of product
        $product->setVisibility(4); // visibilty of product (catalog / search / catalog, search / Not visible individually)
        $product->setTaxClassId(0); // Tax class id
        $product->setTypeId('simple'); // type of product (simple/virtual/downloadable/configurable)
        $product->setPrice(199); // price of product
        $product->setStockData(
                 array(
                      'use_config_manage_stock' => 0,
                      'manage_stock' => 1,
                      'is_in_stock' => 1,
                      'qty' => 99999
                      )
                     );
        $product = $product->save();
        $ID = $product->getId();
        //global $sku;
        $this->sku = $product->getSku(); // here global variable $sku should update
    }

}

Thanks.

Answer 1

I think I'm more going to answer a "php question" than a "magento question" here.

I would have use

$this->sku

and declare it with the others (protected $resultPageFactory;protected $session;private $productRepository;)

Its value will be updated in the object rather than in the method.

I Hope I'm clear enough ;)

If not, there is the documentation. https://www.php.net/manual/fr/language.oop5.properties.php

Answer 2

I solved problem using core session to store value and access globally, here is example to understand concept:

use Magento\Framework\Session\SessionManagerInterface as CoreSession;

class MyClass
{

protected $_coreSession;

public function __construct(
    ...
    CoreSession $coreSession
    ...
) {
    $this->_coreSession = $coreSession;
}

public function setValue(){
    $this->_coreSession->start();
    $this->_coreSession->setMyVariable('My variable value');
}
}

Get your variable value anywhere by core session as:

public function getValue(){
    $this->_coreSession->start();
    return $this->_coreSession->getMyVariable();
}

We can also unset session variable by

public function unsetValue(){
    $this->_coreSession->start();
    return $this->_coreSession->unsMyVariable();
}