Error: Could not generate the preview – due to the string “<?php"

When I save the PHP code in backend. I get the error: Could not generate the preview.

Finally I found out, that one of the ModSec security rules of my provider (hoststar.ch) prohibited saving of the code. Temporarely disabling ModSec solved the problem.

In case other users of the wonderful plugin have similar problems, it would be helpful, if the plugin would substitute the appearance of the string “<?php” by something else on uploading (and recovr it after uploading).

Or is there another solution besides disabling security rules?