drupal_goto in new tab Shortly: How can I open a drupal_goto() result in a new tab?

More details:

I've got a list of news, made with Views, that can be imported from a RSS feed (big custom module, very complicated, etc, etc) or directly written by the site's editor.

When I click on a news, I access the node full view mode page and, if it is an imported news, I'm redirected to the source site with drupal_goto(source).

I want to redirect to the external source site in another tab. And I can't figure it out. I'm not even sure if that's possible with only PHP.

Thanks in advance for any help.
That isn't possible - drupal_goto() happens server-side, and you can only affect tabs/windows with client-side code.

You would need to stop using drupal_goto(), and instead insert some javascript into the page which opens the new URL in a new tab upon refresh.

Some (including myself) would also argue that you have no "right" to do this - let the user decide whether they want a new tab or not. Be careful of trying to force your will onto them. See Target Blank is Evil for a wonderfully opinionated bit of rhetoric on the matter.