Remove cash on delivery if any product in cart is on backorder - WooCommerce

functions.php

function remove_cod_if_backorder( $available_gateways ) {
    if ( !is_array( $available_gateways ) ) return;

    foreach ( WC()->cart->get_cart() as $cart_item ) {
        $product = $cart_item['data'];
        if ( $product && $product->is_on_backorder( $cart_item['quantity'] ) ) {

            unset( $available_gateways['cod'] );
            break;
        }
    }
    return $available_gateways;
}
add_filter( 'woocommerce_available_payment_gateways', 'remove_cod_if_backorder' );