add action when order is compltete code example

Example: woocommerce action order complete

function mysite_woocommerce_order_status_completed( $order_id ) {
    error_log( "Order complete for order $order_id", 0 );
}
add_action( 'woocommerce_order_status_completed', 'mysite_woocommerce_order_status_completed', 10, 1 );