Add Entry ID to Order

Here's how you can implement this:

### Steps:

1. **Capture `entry_id` from the Add-to-Cart Process**
Ensure that `entry_id` is passed along with the product when it is added to the cart. You can use `woocommerce_add_cart_item_data` to add custom data to the cart.

2. **Save `entry_id` in Order Meta**
When the order is created, you can use the `woocommerce_checkout_create_order` hook to add the `entry_id` to the postmeta table.

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### Code Example:

Add the following code to your theme's `functions.php` file or a custom plugin:

// Step 1: Add `entry_id` to cart item data
add_filter('woocommerce_add_cart_item_data', function($cart_item_data, $product_id, $variation_id) {
    if (isset($_GET['entry_id'])) {
        $cart_item_data['entry_id'] = sanitize_text_field($_GET['entry_id']);
    }
    return $cart_item_data;
}, 10, 3);

// Step 2: Display `entry_id` in cart and checkout (optional for debugging)
add_filter('woocommerce_get_item_data', function($item_data, $cart_item) {
    if (isset($cart_item['entry_id'])) {
        $item_data[] = array(
            'name' => __('Entry ID'),
            'value' => $cart_item['entry_id'],
        );
    }
    return $item_data;
}, 10, 2);

// Step 3: Save `entry_id` to order meta
add_action('woocommerce_checkout_create_order_line_item', function($item, $cart_item_key, $values, $order) {
    if (isset($values['entry_id'])) {
        $item->add_meta_data('entry_id', $values['entry_id']);
    }
}, 10, 4);

// Step 4: Save `entry_id` as post meta in the order (if needed at the order level)
add_action('woocommerce_checkout_update_order_meta', function($order_id, $data) {
    $order = wc_get_order($order_id);
    $entry_ids = [];
    foreach ($order->get_items() as $item) {
        if ($entry_id = $item->get_meta('entry_id')) {
            $entry_ids[] = $entry_id;
        }
    }
    if (!empty($entry_ids)) {
        update_post_meta($order_id, '_entry_ids', implode(',', $entry_ids)); // Save as comma-separated values
    }
}, 10, 2);

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### Explanation:

1. **Step 1: Add `entry_id` to Cart Item Data**
– The `woocommerce_add_cart_item_data` filter captures the `entry_id` from the URL query string and attaches it to the cart item.

2. **Step 2: Display `entry_id` (Optional)**
– This step adds `entry_id` to the cart and checkout display for debugging or customer visibility.

3. **Step 3: Save `entry_id` to Order Line Item**
– The `woocommerce_checkout_create_order_line_item` hook ensures the `entry_id` is saved as part of each product line item in the order.

4. **Step 4: Save `entry_id` in Order Meta**
– If you need to save all `entry_id` values associated with an order at the order level, this step updates the order meta.

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### Verifying the Data:
1. Check the WooCommerce order meta via the WordPress Admin under **WooCommerce > Orders**.
2. Use a tool like phpMyAdmin to verify the data in the `wp_postmeta` table, where the `_entry_ids` meta key should be stored for the order.

Let me know if you need further assistance!

Here’s how you can handle it:

—

### Updated Code

Place the following code in your theme’s `functions.php` or a custom plugin file:

// Step 1: Add `entry_id` to cart item data
add_filter('woocommerce_add_cart_item_data', function ($cart_item_data, $product_id, $variation_id) {
    if (isset($_GET['entry_id'])) {
        $cart_item_data['entry_id'] = sanitize_text_field($_GET['entry_id']);
    }
    return $cart_item_data;
}, 10, 3);

// Step 2: Save `entry_id` directly in the order's postmeta for COD and other payment methods
add_action('woocommerce_checkout_update_order_meta', function ($order_id) {
    // Loop through order items to get the entry_id
    $order = wc_get_order($order_id);
    $entry_ids = [];
    foreach ($order->get_items() as $item) {
        if ($entry_id = $item->get_meta('entry_id')) {
            $entry_ids[] = $entry_id;
        }
    }

    // Save entry_id(s) in postmeta
    if (!empty($entry_ids)) {
        update_post_meta($order_id, '_entry_ids', implode(',', $entry_ids)); // Save as comma-separated values
    }
}, 10, 1);

// Step 3: Add `entry_id` to each order item (ensures it's saved properly for each product line item)
add_action('woocommerce_checkout_create_order_line_item', function ($item, $cart_item_key, $values, $order) {
    if (isset($values['entry_id'])) {
        $item->add_meta_data('entry_id', $values['entry_id']);
    }
}, 10, 4);

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### How It Works

1. **Cart Item Data**: The `entry_id` is captured when the product is added to the cart via the `woocommerce_add_cart_item_data` filter.

2. **Order Line Item Meta**: The `entry_id` is added to the individual order items using the `woocommerce_checkout_create_order_line_item` hook.

3. **Order Meta Update**: Once the order is created, the `woocommerce_checkout_update_order_meta` hook saves the `entry_id` into the order’s meta (in the `postmeta` table) alongside other metadata.

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### Why This Works for Cash on Delivery
The `woocommerce_checkout_update_order_meta` hook runs during the checkout process, regardless of the payment method (e.g., Cash on Delivery, PayPal, etc.). It saves the metadata when the order is created, ensuring the `entry_id` is stored immediately.

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### Verification
– After placing a COD order, check the `wp_postmeta` table for the `_entry_ids` meta key associated with the order ID.
– Alternatively, check the WooCommerce Admin:
– Go to **WooCommerce > Orders**.
– Open the specific order and look at the **Custom Fields** section to verify the saved `entry_id`.

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### Additional Considerations
– If the `entry_id` needs to be used for reporting or analytics, store it in a format that is easy to query (e.g., as a serialized array or comma-separated values).
– Ensure the `_entry_ids` key is unique and does not conflict with other postmeta keys.

Let me know if you encounter any issues!