I would like to add php code in the right sidebar.

Could anyone tell me how to achieve this please?

Thanks in advance.

Get a plugin like Exec-Php or Samsarin PHP, which lets you execute PHP in a widget. Once the plugin is activated, you can use a Text widget, put it in a sidebar, paste in the PHP code, and save the widget.

Thanks paulae.
I did not know Exec-Php before.
It works for me.
Regards.