Code-Snippets-Functions/Execute a function on a child site/WooCommerce/disable-place-order-for-out-of-stock-products.txt

function wc_check_cart_item_stock() {
    $product_qty_in_cart      = WC()->cart->get_cart_item_quantities();
    $current_session_order_id = isset( WC()->session->order_awaiting_payment ) ? absint( WC()->session->order_awaiting_payment ) : 0;

    // Loop through cart items
    foreach ( WC()->cart->get_cart() as $cart_item_key => $values ) {
        $product = $values['data'];

        // Check stock based on stock-status.
        if ( ! $product->is_in_stock() ) {
            return false;
        }

        // We only need to check products managing stock, with a limited stock qty.
        if ( ! $product->managing_stock() || $product->backorders_allowed() ) {
            continue;
        }

        // Check stock based on all items in the cart and consider any held stock within pending orders.
        $held_stock     = wc_get_held_stock_quantity( $product, $current_session_order_id );
        $required_stock = $product_qty_in_cart[ $product->get_stock_managed_by_id() ];

        if ( $product->get_stock_quantity() < ( $held_stock + $required_stock ) ) {
            return false;
        }
    }
    return true;
}

add_filter( 'woocommerce_order_button_html', 'disable_order_button_html' );
function disable_order_button_html( $button ) {
    if( wc_check_cart_item_stock() ) {
        return $button;
    } else {
        return '<a class="button alt disabled" style="cursor:not-allowed; text-align:center">' .__('Place order', 'woocommerce') . '</a>';
    }
}