PHP in Templates and Template Conditionals

[gokufg]

the code

<if !$GLOBALS['my_first_post'] && ($GLOBALS['my_first_post'] = true) then>
first post in forum id 1
</if>

It's ok and works

EDIT

I tried to insert in forum template

<if ($GLOBALS['forum']['fid'] == 36 || $GLOBALS['foruminfo']['fid'] == 36) then>
first post in forum id 36
</if>

and the "first post in forum id 36" showed in that forum... But I'd like show "first post in forum id 36" in all threads of forum 36 and i all subforums. Do you understand?