XHTML Content Negotiation Examples

The following are scripting examples of content negotiation using the HTTP Accept header.

These examples are used to properly serve XHTML with the proper MIME media type of application/xhtml+xml. If the request header does not allow this media type, it will be served as text/html. This convention follows the W3C standard for “Recommended Media Type Usage:”

1. If the Accept header explicitly contains application/xhtml+xml (with either no “q” parameter or a positive “q” value) deliver the document using that media type.
2. If the Accept header explicitly contains text/html (with either no “q” parameter or a positive “q” value) deliver the document using that media type.
3. If the accept header contains “*/*” (a convention some user agents use to indicate that they will accept anything), deliver the document using text/html.

Apache .htaccess file

HTACCESSview code

RewriteCond %{HTTP_ACCEPT} application/xhtml\+xml
RewriteCond %{HTTP_ACCEPT} !application/xhtml\+xml\s*;\s*q=0\.?0*(\s|,|$)
RewriteCond %{REQUEST_URI} \.html$
RewriteRule .* - [T=application/xhtml+xml;charset=utf-8]
RewriteCond %{HTTP_ACCEPT} application/xhtml\+xml
RewriteCond %{HTTP_ACCEPT} !application/xhtml\+xml\s*;\s*q=0\.?0*(\s|,|$)
RewriteCond %{REQUEST_URI} !\.
RewriteRule .* - [T=application/xhtml+xml;charset=utf-8]

PHP

PHPview code

<?php
    if ( stristr($_SERVER["HTTP_ACCEPT"],"application/xhtml+xml") ) {
        header("Content-type: application/xhtml+xml");
    } else {
        header("Content-type: text/html");
    }
?>

CGI Script

CGIview code

import os
if os.environ.get('HTTP_ACCEPT', '').find('application/xhtml+xml') > -1:
    print 'Content-type: application/xhtml+xml'
else: print 'Content-type: text/html'

Ruby (for rails)

RUBYview code

<%
if @request.env["HTTP_ACCEPT"].index('application/xhtml+xml')
@headers["Content-Type"] = "application/xhtml+xml; charset=utf-8"
else
@headers["Content-Type"] = "text/html; charset=utf-8"
end
%>