Cannot find self class!!!!

[techu]

When we call a static function we use self:: instead of $this to call the function. But I get an error that the class self is not found when I uploaded my script on my host. But it works perfectly on localhost.

Host is running redhat php 5.2.12

localhost running windows php5.3
I also tested it on ubuntu php5.3, and it works fine.

any idea anyone why this is happening?
Is it that php 5.2.12 does not support self:: or something?