PHP (<? wont work, but <?php will)

[exploitations]

I've created a social network under xampp linux, and most of my scripts I used "<?" instead of "<?php".
Under windows, when the codes are "<?" it displays the whole code as text. With "<?php" is displays correctly.
I never had this problem before, why the change?
Does anybody know how to fix it?

Thank you,
Bailey

[Altrea]

see your other post