PHP Markdown Extra Math

[Dr. Drang]

This is a minor extension to Michel Fortin's work that helps me add
equations using LaTeX syntax (via jsMath) to my blog posts. It's based
on v. 1.2.4. There's a brief description here

http://www.leancrew.com/all-this/2009/12/php-markdown-extra-math/

and the GitHub repository is here

http://github.com/drdrang/php-markdown-extra-math

The display math code seems fairly clean to me, but the inline math is
a bit messy, as I had to pry open Michel's handleSpanToken function.
The code works for me, but suggestions for improvement are welcome.