xwiki removes code from php macro

When I am trying to add php macro from the example:

{{php}}<?php echo 'Hello World!'; ?>{{/php}}

to the empty page on my xwiki instance I can see the result "Hello World!"  in WYSIWYG of CKEditor. But when I'm trying to save and preview the page I see nothing on it. When I switch back to editor I see only:

{{php}}{{/php}}

in the source. Everything I put outside of the

<? ?>

symbols stays untouched.