there's some problem with your patch :
abs: returns number, not mixed
we don't use "number" but "int" or "float"
Well, we use "number", or at least it is documented that we use that in case any number is acceptable as a parameter...
http://www.php.net/manual/en/language.pseudo-types.php
Oh yes, something else : I'm not sure but if you name your patch "stg.txt" it will be displayed inline with your message in most mail reader (mine, btw ;)). It will be a little be handy to quick view it.
Most mail clients know TXT and attach it as plain text. In case of an unknown extension, a binary encoding is used mostly...
Goba