<?php

     /* doctype.php -- DOCTYPE HTML 4.01 and XHTML 1.0/1.1
                       Transitional, Frameset and Strict
                       also performs content-type negotiation

    (c) Copyright 2004-2006, Douglas W. Clifton, all rights reserved.
        for more copyright information visit the following URI:
        http://loadaveragezero.com/info/copyright.php */

    $agent = get_browser(null, true);  // user agents don't play nice

    // and this one is the biggest bully in the schoolyard

    $_IE = ($agent['browser'] == 'IE');

    $media = array(
        'HTML'  => 'text/html',
        'XHTML' => 'application/xhtml+xml'
    );

    $charset = 'UTF-8';     // Unicode 8-bit character encoding
    $lang    = 'en-US';     // US English

    function doctype($doc = 'xhtml', $type = 'strict', $ver = '1.1') {

        global $media, $media_type;     // these we share with head(), etc.

        $doc  = strtoupper($doc);
        $type = strtolower($type);

        $avail = 'PUBLIC';  // or SYSTEM, but we're not going there yet

        // begin FPI

        $ISO = '-';     // W3C is not ISO registered [or IETF for that matter]
        $OID = 'W3C';   // unique owner ID
        $PTC = 'DTD';   // the public text class

        // as far as I know the PCL is always English

        $PCL = 'EN';
        $xlang = 'en';  // this you may want to vary if you're in different locale

        // DTDs are all under the Technical Reports (TR) branch @ W3C

        $URI  = 'http://www.w3.org/TR/';

        $doc_top  = '<html';    // what comes after the DOCTYPE of course

        if ($doc == 'HTML') {

            $top = $doc;
            $media_type = $media[$doc];

            $PTD = $doc . ' 4.01';  // we're only supporting HTML 4.01 here

            switch ($type) {

                case 'frameset':

                    $PTD .= ' ' . ucfirst($type);
                    $URI .= 'html4/frameset.dtd';
                    break;

                case 'transitional':

                    $PTD .= ' ' . ucfirst($type);
                    $URI .= 'html4/loose.dtd';
                    break;

                case 'strict':
                default:

                    $URI .= 'html4/strict.dtd';
            }
            $doc_top .= '>';   // no namespaces here
        }
        else {

            // must be xhtml then, but catch typos

            if ($doc != 'XHTML') $doc = 'XHTML';

            $top = 'html';  // remember XML is lowercase
            $doc_top .= ' xmlns="http://www.w3.org/1999/xhtml" xml:lang="' . $xlang . '"';

            // return the correct media type header for this document,
            // but we should probably make sure the browser groks XML!

            // the W3C validator does not send the correct Accept header for this family of documents, sigh

            if (stristr($_SERVER['HTTP_USER_AGENT'], 'W3C_Validator')) $media_type = $media['XHTML'];
            else $media_type = (stristr($_SERVER['HTTP_ACCEPT'], $media['XHTML'])) ? $media['XHTML'] : $media['HTML'];

            // do NOT send XHTML 1.1 to browsers that don't accept application/xhtml+xml
            // see: labs/PHP/DOCTYPE.php#bug-fix for details and a link to the W3C XHTML
            // NOTES on this topic

            if ($media_type == $media['HTML'] and $ver == '1.1') $ver = '1.0';

            if ($ver == '1.1') {
                $PTD = implode(' ', array($doc, $ver));
                $URI .= 'xhtml11/DTD/xhtml11.dtd';
            }
            else {
                $PTD = implode(' ', array($doc, '1.0', ucfirst($type)));
                $URI .= 'xhtml1/DTD/xhtml1-' . $type . '.dtd';

                // for backwards compatibilty
               
                $doc_top .= ' lang="' . $xlang . '"';
            }

            $doc_top .= '>';    // close root XHTML tag

            global $_IE, $charset, $lang;

            // send HTTP header

            header('Content-type: ' . $media_type . '; charset=' . $charset);

            // send the XML declaration before the DOCTYPE, but this
            // will put IE into quirks mode which we don't want

            if (!$_IE) echo '<?xml version="1.0" encoding="' . $charset . '"?>' . "\n";
        }

        $FPI = implode('//', array($ISO, $OID, $PTC . ' ' . $PTD, $PCL));

        echo <<<_DTD
    <!DOCTYPE $top
              $avail
             "$FPI"
             "$URI">
    $doc_top

_DTD;

    } // doctype()

    // doctype.php
?>