On a WordPress page I use only a shortcode with the following PHP code with inserted HTML:
The code is running correctly. When I insert the two line (see picture) I get a 404 message. The URL is shown correctly. When I click on the Edit page the page which should be invoked by the action is shown.
I have similar effects with other pages? What do I make wrong???
Read more here: Getting a 404 using a php / HTML shrotcode