Problem in executing PHP

I’m using WordPress 2.2.1 and using Exec-PHP to run PHP. I wrote
<?php echo "This is the Exec-PHP 'Hello World'"; ?>

in the write page box (not in visual editor) and the result I got was

< ?php echo “This is the Exec-PHP ‘Hello World’”; ?>

A space in between <?php, like this < ?php

It isn’t displaying correctly. I’m this same problem with all such plugins which allow executing of PHP.

Please help me how to fix this error.