Setting headers in a PHP include directive

I am currently working on a project that uses a PHP CMS for the bulk of the site. However, it pulls some content from a page generated by JSTL on a tomcat. I was using the fmt tag to do some pretty printing of numbers, and it looked fine when I viewed the content as served by tomcat. However, none of the formatting was carrying through when the PHP page included the jsp. Why? It appears that the fmt tag needs a locale. I confirmed that with wget.

Now, how to set the header with the PHP include. The include man page was no help, and mod_rewrite won’t let you modify headers, as far as I can tell. Once the request arrived to tomcat, that was too late.

Some digging around in the PHP documentation on fopen turned up this gem:

Custom headers may be sent with an HTTP request prior to version 5 by taking advantage of a side-effect in the handling of the user_agent INI setting. Set user_agent to any valid string (such as the default PHP/version setting) followed by a carriage-return/line-feed pair and any additional headers. This method works in PHP 4 and all later versions.

Click through for a code example. The aforementioned documentation talks about custom headers, but it worked for sending the Accept-Language header that the fmt tags needed.