Set Default Stock Inventory Backorder Setting in Woo

This code sets your single product > inventory > stock management setting to allow by default. On your inventory tab, it does 3 things :

1. Sets the Stock Management checkbox to yes enabling you to track stock quantity for this product.
2. Sets the Allow Backorders radio button to “Allow” by default on all single product pages.
3. Enables the default settings to be changed per product ( use 2nd snippet ).

Here’s the result, click to enlarge :

Here’s a demo video showing how the 1st snippet works :

There’s 2 code snippets in this tutorial :

1. The 1st snippet sets the default so it cannot be changed manually on any single product
2. The 2nd snippet sets the default and allows manually changing of the settings on a per product page basis.

Add the following code to the end of your child themes functions.php file or custom code snippets plugin.

add_action('woocommerce_product_options_inventory_product_data', 'set_default_stock_management_and_backorder_setting_06');
add_action('woocommerce_process_product_meta', 'save_default_stock_management_and_backorder_setting_06');

function set_default_stock_management_and_backorder_setting_06() {
    global $post;

    // Check if we are editing an existing product
    if ($post && get_post_type($post->ID) === 'product') {
        ?>
        <script type="text/javascript">
            jQuery(document).ready(function($) {
                // Check the "Manage stock?" checkbox
                var manageStockCheckbox = $('#_manage_stock');
                if (!manageStockCheckbox.is(':checked')) {
                    manageStockCheckbox.prop('checked', true).trigger('change');
                }

                // Set default value for backorders to "Allow"
                var backordersAllow = $('input[name="_backorders"][value="yes"]');
                var backordersNotify = $('input[name="_backorders"][value="notify"]');
                var backordersNo = $('input[name="_backorders"][value="no"]');

                if (backordersNo.is(':checked') || backordersNotify.is(':checked')) {
                    backordersAllow.prop('checked', true);
                }
            });
        </script>
        <?php
    }
}

function save_default_stock_management_and_backorder_setting_06($post_id) {
    $product = wc_get_product($post_id);

    // Enable stock management
    if (!$product->get_manage_stock()) {
        update_post_meta($post_id, '_manage_stock', 'yes');
    }

    // Set default backorder setting to "Allow" if it's not already set
    if ($product->get_backorders() !== 'yes') {
        update_post_meta($post_id, '_backorders', 'yes');
    }
}

However, you might want to change the settings manually on some products. In this case, use the following code snippet instead.

add_action('admin_init', 'set_default_stock_management_and_backorder_for_existing_products_once');

function set_default_stock_management_and_backorder_for_existing_products_once() {
    // Check if we have already set defaults
    $defaults_set = get_option('defaults_set_for_existing_products');

    if (!$defaults_set) {
        // Get all products
        $args = array(
            'post_type' => 'product',
            'posts_per_page' => -1,
        );

        $products = new WP_Query($args);

        if ($products->have_posts()) {
            while ($products->have_posts()) {
                $products->the_post();
                $product_id = get_the_ID();
                $product = wc_get_product($product_id);

                // Enable stock management if not already enabled
                if ($product && !$product->get_manage_stock()) {
                    update_post_meta($product_id, '_manage_stock', 'yes');
                }

                // Set default backorder setting to "Allow" if not already set
                if ($product && $product->get_backorders() !== 'yes') {
                    update_post_meta($product_id, '_backorders', 'yes');
                }
            }
            wp_reset_postdata();

            // Mark defaults as set
            update_option('defaults_set_for_existing_products', true);
        }
    }
}

The code can be customized to do anything you like!