Server side include`s problem

[uuganbat]

HI all

In RH 9.0 I installed apache web server and php, mysql. All things
working fine php scripts are working fine.
But one problem is occurred. SSI (server side include) is not working
only code is printed. Example
<!-- include("filename.php"); -->     not executing php file only
printing php source codes. So I replaced this code bye <?php
include("filename.php"); ?> this is executing fine. 
I think this is SSI problem how to solve.
							Sorry me, my
English is poor.

Best Regards