WooCommerce - Don't allow shipping to PO Box addresses

woocommerce-deny-pobox-shipping

add_action('woocommerce_after_checkout_validation', 'deny_pobox_postcode');
 
function deny_pobox_postcode( $posted ) {
  global $woocommerce;
  
  // Put postcode, address 1 and address 2 into an array
  $check_address  = array();
  $check_address[] = isset( $posted['shipping_postcode'] ) ? $posted['shipping_postcode'] : $posted['billing_postcode'];
  $check_address[] = isset( $posted['shipping_address_1'] ) ? $posted['shipping_address_1'] : $posted['billing_address_1'];
  $check_address[] = isset( $posted['shipping_address_2'] ) ? $posted['shipping_address_2'] : $posted['billing_address_2'];
 
  // Implode address, make lowercase, and remove spaces and full stops
  $check_address = strtolower( str_replace( array( ' ', '.' ), '', implode( '-', $check_address ) ) );
 
  if ( strstr( $check_address, 'pobox' ) ) {
    $woocommerce->add_error( "Sorry, we don't ship to PO BOX addresses." );
  }
}