D7 CCK default values and PHP input
Drupal 7 is a lot different than Drupal 6 in many ways. What used to be called CCK, now called "fields in core" or "fields" is also different. Not all of the features that was in CCK is available in Drupal 7 fields, some are, but contrib modules is needed.

Regarding using PHP default values, I don't know of a module that does this. It's possible with hook_form_alter in a custom module, but this might not be what you are looking for.

I don't know of any way to gray out fields when editing an entity, other than again using hook_form_alter. The field permissions module might be able to help you, to deny users the ability to edit the field. It would then disappear entirely, but that could be a possible solution.