(in perl)
print 'P3P: policyref="/w3c/p3p.xml"\n';
print "content-type: text/html\n\n";
(in PHP)
<? header('P3P: policyref="/w3c/p3p.xml"');?>
I've not tested this, but seems like it should work?
[httpd.apache.org...]
If you can place files into the directory where your HTML files are, put a .htaccess file there containing a line similar to this:
Header set P3P "policyref=\"/w3c/p3p.xml\""
This obviously assumes that mod_headers is available, and you may have to fiddle with the quotes until it really does what you need. It will have effect on the local directory, as well as all of its subdirectories where you don't specify something else.