[Orgmode] First line of exported HTML causes error as .php

[Dan Davison]

I think there's been a change in HTML export which has broken the way in
which I was using org to produce PHP files. The HTML exporter now
produces the following as the first line (I believe this is new).

<?xml version="1.0" encoding="iso-8859-1"?>

However, when the file is produced with a .php suffix

(setq org-export-html-extension "php")

and placed on a PHP-enabled web server, I get this error:

Parse error: syntax error, unexpected T_STRING in
/net/markov/export/postdocs/davison/pub_html/software/shellfish/shellfish.php
on line 1

It seems to work OK if I delete the first line. I know next to nothing
about these things and I'd appreciate it if someone could tell me
whether this should be viewed as a bug in org, or whether I am just
doing things the wrong way. (Is this how others produce PHP files in
org?)

Thanks,

Dan