Recovered from the Wayback Machine.
I didn’t know the ?> closing tag was optional with PHP code only files, either. I did know about white space following the end tag. Probably every PHP developer knows about the white space following the end tag problem.
What header? What ******** header!?
Other useful stuff on PHP best practices at the Drupal site, with more detail on omitting the end tag.
Question to those who know Drupal: how is it on supporting XHTML? Both published and consumed via comments?