Why don't documents have the ending php tag?

I see that many components, controllers etc all start with <?php but not ending with ?>, why is that?

I know that this is not necessary. Necessarily the only opening tag.

Yes I know that as well, it's quite obvious since it all comes like that out of the box, but my question is why, and if this is docuemented somewhere?


"For files that contain only PHP code, the closing tag ("?>") is never permitted. It is not required by PHP, and omitting it prevents the accidental injection of trailing white space into the response."