WooCommerce Cart Initialization Error

function pmm_empty_cart_mobile_fragment($fragments)
{
if (WC()->cart && WC()->cart->get_cart_contents_count() === 0) {
$fragments['.wc-proceed-to-checkout-mobile'] = 'Proceed to checkout ';
}
return $fragments;
}

### Problem Analysis
Your code snippet shows a custom fragment handler function `pmm_empty_cart_mobile_fragment`. It's likely hooked to a filter or action, and if that hook runs too early in the WordPress lifecycle, `WC()->cart` might not be properly initialized.

The key issue is that WooCommerce relies on the `wp_loaded` action to initialize its core functionality. Accessing `WC()->cart` before this point triggers an error.

### Solution
1. **Delay the execution of your code**: Ensure your custom function is hooked to an appropriate action that runs after `wp_loaded`.

2. **Example of Proper Hook Usage**: If you're using this function to modify WooCommerce fragments, it should be hooked into a WooCommerce-compatible filter, such as `woocommerce_update_order_review_fragments`.

### Revised Code

function pmm_empty_cart_mobile_fragment($fragments) {
    // Ensure WooCommerce is initialized
    if (WC()->cart && WC()->cart->get_cart_contents_count() === 0) {
        $fragments['.wc-proceed-to-checkout-mobile'] = '<a href="/checkout/" style="display:none;" class="checkout-button button alt wc-forward">Proceed to checkout <span class="woocommerce-Price-amount amount"></span></a>';
    }
    return $fragments;
}

// Hook the function to the correct WooCommerce fragment update filter
add_filter('woocommerce_update_order_review_fragments', 'pmm_empty_cart_mobile_fragment');

### Key Points
– **Proper Filter Usage**: `woocommerce_update_order_review_fragments` is invoked when WooCommerce updates the checkout order review fragments, ensuring WooCommerce is fully loaded.
– **Avoid Direct Invocation Before `wp_loaded`**: Ensure any functions interacting with `WC()->cart` or other WooCommerce classes are hooked to appropriate actions or filters that run after `wp_loaded`.

### Debugging Tips
– If issues persist, use `error_log()` to verify when your function is running relative to `wp_loaded`:

add_action('wp_loaded', function() {
      error_log('WP Loaded');
  });
  error_log('Function execution started');

This will help you confirm the order of execution and adjust accordingly.

### Analysis
This approach is generally fine if it runs in a context where WooCommerce is fully loaded and initialized. However, the `is_cart()` and `WC()->cart` methods depend on WooCommerce being properly initialized. If this code is executed too early (e.g., in a template that runs before `wp_loaded` or outside of WooCommerce-compatible hooks), it might lead to errors like the one in your original question.

### Improvements
1. **Ensure WooCommerce is Fully Loaded**:
Use hooks or conditions to ensure this code runs at the appropriate time in the WordPress lifecycle. For instance:
– Place this code in a WooCommerce-compatible template file like `cart.php`.
– Use the `woocommerce_before_cart` or `woocommerce_after_cart` hooks if you're adding this via a custom plugin or theme.

2. **Sanitize Output**:
Use `esc_html()` or `esc_attr()` to sanitize the output for better security.

3. **Check for Initialization**:
Wrap your logic with a check to ensure `WC()->cart` is initialized before accessing its methods.

### Revised Code Example

if (function_exists('is_cart') && is_cart() && WC()->cart && WC()->cart->get_cart_contents_count() > 0) { ?>
    <div class="wc-proceed-to-checkout wc-proceed-to-checkout-mobile">
        <a href="/checkout/" class="checkout-button button alt wc-forward">
            Proceed to checkout 
            <span class="woocommerce-Price-amount amount">
                <?php echo esc_html(WC()->cart->get_total()); ?>
            </span>
        </a>
    </div>
<?php }

### Key Points
– **`function_exists('is_cart')`**: Ensures the function is available to avoid fatal errors in non-WooCommerce contexts.
– **Sanitize Output**: `esc_html()` ensures that the total amount is safe to output in HTML.
– **Proper Hook Usage**: If this code is being added dynamically (e.g., via a plugin), hook it to an appropriate WooCommerce action like `woocommerce_before_cart`.

### Debugging Tip
If you're adding this code dynamically and still encounter initialization issues, log errors to debug WooCommerce's readiness:

if (!WC()->cart) {
    error_log('WC()->cart is not initialized');
}

// Check if PayPal should be disabled for the current product
$disable_paypal = get_post_meta($product_id, '_disable_paypal', true);

if ($disable_paypal === 'yes') {
unset($available_gateways['ppcp-gateway']);
break; // Exit the loop once PayPal is disabled
}
}
}

return $available_gateways;
}

—

### What the Code Does
1. **Filter Hook**: It hooks into the `woocommerce_available_payment_gateways` filter to modify the list of available payment gateways.
2. **Admin and Cart Checks**: It bypasses the filter logic if:
– The request is made in the admin area (`is_admin()`).
– WooCommerce is not initialized (`!WC()->cart`).
3. **Iterates Through Cart Items**: If the cart is not empty, it loops through the cart items to check if any product has a `_disable_paypal` meta key set to `'yes'`.
4. **Disables PayPal**: If a product in the cart has the `_disable_paypal` meta key set to `'yes'`, it removes the PayPal gateway (`ppcp-gateway`) from the `$available_gateways` array.

—

### Potential Pitfalls
1. **Gateway Key**: Ensure the `ppcp-gateway` key matches the actual key used for PayPal in your WooCommerce setup. This can vary based on the PayPal plugin you're using (e.g., `paypal` for standard or `ppcp-gateway` for PayPal Commerce).
2. **Meta Key `_disable_paypal`**: Ensure the `_disable_paypal` meta key is properly set up in your product meta. If it's missing or misnamed, this logic won't work.
3. **Performance**: If the cart has many items, looping through all of them might introduce minor performance overhead. This is usually negligible unless dealing with very large carts or complex meta lookups.

—

### Improvements and Best Practices
1. **Hook Priority**: Use a priority for the `add_filter` call to ensure it executes after other modifications to payment gateways:

add_filter('woocommerce_available_payment_gateways', 'pmmv1_disable_paypal_for_specific_products', 20);

2. **Early Return for Empty Carts**: Simplify the logic slightly to improve readability:

if (is_admin() || !WC()->cart || WC()->cart->is_empty()) {
       return $available_gateways;
   }

3. **Use `wc_get_product` for Better Flexibility**:
Instead of `get_post_meta`, you could use `wc_get_product` for more robust product data handling:

$product = wc_get_product($product_id);
   $disable_paypal = $product->get_meta('_disable_paypal');

4. **Debugging**: Add logging for debugging purposes to confirm the gateway is removed when expected:

if ($disable_paypal === 'yes') {
       error_log("PayPal disabled for product ID: $product_id");
       unset($available_gateways['ppcp-gateway']);
       break;
   }

—

### Final Refined Code

add_filter('woocommerce_available_payment_gateways', 'pmmv1_disable_paypal_for_specific_products', 20);
function pmmv1_disable_paypal_for_specific_products($available_gateways)
{
    if (is_admin() || !WC()->cart || WC()->cart->is_empty()) {
        return $available_gateways;
    }

    foreach (WC()->cart->get_cart() as $cart_item) {
        $product_id = $cart_item['product_id'];

        // Check if PayPal should be disabled for the current product
        $product = wc_get_product($product_id);
        $disable_paypal = $product->get_meta('_disable_paypal');

        if ($disable_paypal === 'yes') {
            unset($available_gateways['ppcp-gateway']);
            error_log("PayPal disabled for product ID: $product_id");
            break; // Exit the loop once PayPal is disabled
        }
    }

    return $available_gateways;
}

—

### Testing
1. **Set Meta Key for Products**: Ensure products you want to exclude PayPal for have `_disable_paypal` meta key set to `'yes'`. You can set this in the product editor or programmatically:

update_post_meta($product_id, '_disable_paypal', 'yes');

2. **Check Payment Gateways**: Add a product with `_disable_paypal` set to `'yes'` to the cart and verify PayPal doesn't appear as a payment option at checkout.
3. **Log Review**: Check the debug logs for the message confirming PayPal was disabled:

PayPal disabled for product ID: [product_id]

With these improvements and checks, your code should function reliably in a WooCommerce environment.