How to find 1st post in a thread

[Thr33]

Im trying to code an action into just the original post of a thread but not in replies. So for a new thread it will do something, but when replying in that thread it does something else. Ive been looking through similar related topics but can only find code written in older versions of vbulletin.

Example (in functions_newpost.php)

PHP Code:

if $postinfo['postid'] == 0 


This is Vbulletin 3.5 for finding the first post in a thread, but it dosnt work in Vbulletin 4.0+

Can anyone help?