Syntax highlighting issue?

Question

Am I doing something incorrectly in the following answer: Retrieving all Links from a Post?

In the edit view the code highlights as expected, but in the answer the code is just red.

Answer 1

Thanks to Jan Fabry, I figured this out. The post was taged "regex", so the syntax highlighting defaulted to regex mode. Jan modified my post so that, just before the code block, there was the following comment tag:

<!-- language: lang-php -->

This reset the highlighting.

Answer 2

Add opening <?php tags.

(Why do I have to add extra characters?)