Changing WordPress — installed all the right plugins?
Just wondering are you migrating WordPress? … Did you have a plugin like Exec-PHP allowing PHP content in posts and pages on one install and that plugin is not active in another install of WordPress?
WordPress by default doesn’t allow PHP in posts and pages so this could be your problem.
Check your WordPress database with PHPMyAdmin or any other SQL tool
You should also browse your WordPress database and check if the content is there in one of the posts. It’s not likely that the importer stripped out your code.