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<?php
/**
* The content negotiator performs "text/html" or "application/xhtml+xml" switching.
* It does this through the static function ContentNegotiator::process().
* By default, ContentNegotiator will comply to the Accept headers the clients
* sends along with the HTTP request, which is most likely "application/xhtml+xml"
* (see "Order of selection" below).
*
* Order of selection between html or xhtml is as follows:
* - if PHP has already sent the HTTP headers, default to "html" (we can't send HTTP Content-Type headers any longer)
* - if a GET variable ?forceFormat is set, it takes precedence (for testing purposes)
* - if the user agent is detected as W3C Validator we always deliver "xhtml"
* - if an HTTP Accept header is sent from the client, we respect its order (this is the most common case)
* - if none of the above matches, fallback is "html"
*
* ContentNegotiator doesn't enable you to send content as a true XML document
* through the "text/xml" or "application/xhtml+xml" Content-Type.
* Please see http://webkit.org/blog/68/understanding-html-xml-and-xhtml/ for further information.
*
* @package framework
* @subpackage control
*
* @todo Check for correct XHTML doctype in xhtml()
* @todo Allow for other HTML4 doctypes (e.g. Transitional) in html()
* @todo Make content replacement and doctype setting two separately configurable behaviours - some
* devs might know what they're doing and don't want contentnegotiator messing with their HTML4 doctypes,
* but still find it useful to have self-closing tags removed.
*/
class ContentNegotiator {
protected static $encoding = 'utf-8';
protected static $enabled = false;
/**
* Set the character set encoding for this page. By default it's utf-8, but you could change it to, say, windows-1252, to
* improve interoperability with extended characters being imported from windows excel.
*/
static function set_encoding($encoding) {
self::$encoding = $encoding;
}
/**
* Return the character encoding set bhy ContentNegotiator::set_encoding(). It's recommended that all classes that need to
* specify the character set make use of this function.
*/
static function get_encoding() {
return self::$encoding;
}
/**
* Enable content negotiation for all templates, not just those with the xml header.
*/
static function enable() {
self::$enabled = true;
}
/*
* Disable content negotiation for all templates, not just those with the xml header.
*/
static function disable() {
self::$enabled = false;
}
/**
* Returns true if negotation is enabled for the given response.
* By default, negotiation is only enabled for pages that have the xml header.
*/
static function enabled_for($response) {
$contentType = $response->getHeader("Content-Type");
// Disable content negotation for other content types
if($contentType && substr($contentType, 0,9) != 'text/html' && substr($contentType, 0,21) != 'application/xhtml+xml') return false;
if(self::$enabled) return true;
else return (substr($response->getBody(),0,5) == '<' . '?xml');
}
static function process(SS_HTTPResponse $response) {
if(!self::enabled_for($response)) return;
$mimes = array(
"xhtml" => "application/xhtml+xml",
"html" => "text/html",
);
$q = array();
if(headers_sent()) {
$chosenFormat = "html";
} else if(isset($_GET['forceFormat'])) {
$chosenFormat = $_GET['forceFormat'];
} else {
// The W3C validator doesn't send an HTTP_ACCEPT header, but it can support xhtml. We put this special case in here so that
// designers don't get worried that their templates are HTML4.
if(isset($_SERVER['HTTP_USER_AGENT']) && substr($_SERVER['HTTP_USER_AGENT'], 0, 14) == 'W3C_Validator/') {
$chosenFormat = "xhtml";
} else {
foreach($mimes as $format => $mime) {
$regExp = '/' . str_replace(array('+','/'),array('\+','\/'), $mime) . '(;q=(\d+\.\d+))?/i';
if (isset($_SERVER['HTTP_ACCEPT']) && preg_match($regExp, $_SERVER['HTTP_ACCEPT'], $matches)) {
$preference = isset($matches[2]) ? $matches[2] : 1;
if(!isset($q[$preference])) $q[$preference] = $format;
}
}
if($q) {
// Get the preferred format
krsort($q);
$chosenFormat = reset($q);
} else {
$chosenFormat = "html";
}
}
}
$negotiator = new ContentNegotiator();
$negotiator->$chosenFormat( $response );
}
/**
* Only sends the HTTP Content-Type as "application/xhtml+xml"
* if the template starts with the typical "<?xml" Pragma.
* Assumes that a correct doctype is set, and doesn't change or append to it.
* Replaces a few common tags and entities with their XHTML representations (<br>, <img>, &nbsp;).
*
* @param $response SS_HTTPResponse
* @return string
* @todo More flexible tag and entity parsing through regular expressions or tag definition lists
*/
function xhtml(SS_HTTPResponse $response) {
$content = $response->getBody();
// Only serve "pure" XHTML if the XML header is present
if(substr($content,0,5) == '<' . '?xml' ) {
$response->addHeader("Content-Type", "application/xhtml+xml; charset=" . self::$encoding);
$response->addHeader("Vary" , "Accept");
// Fix base tag
$content = preg_replace('/<base href="([^"]*)"><!--\[if[[^\]*]\] \/><!\[endif\]-->/',
'<base href="$1" />', $content);
$content = str_replace('&nbsp;','&#160;', $content);
$content = str_replace('<br>','<br />', $content);
$content = preg_replace('#(<img[^>]*[^/>])>#i', '\\1/>', $content);
$response->setBody($content);
} else {
return $this->html($response);
}
}
/*
* Sends HTTP Content-Type as "text/html", and replaces existing doctypes with
* HTML4.01 Strict.
* Replaces self-closing tags like <img /> with unclosed solitary tags like <img>.
* Replaces all occurrences of "application/xhtml+xml" with "text/html" in the template.
* Removes "xmlns" attributes and any <?xml> Pragmas.
*/
function html(SS_HTTPResponse $response) {
$response->addHeader("Content-Type", "text/html; charset=" . self::$encoding);
$response->addHeader("Vary", "Accept");
$content = $response->getBody();
$hasXMLHeader = (substr($content,0,5) == '<' . '?xml' );
// Fix base tag
$content = preg_replace('/<base href="([^"]*)" \/>/',
'<base href="$1"><!--[if lte IE 6]></base><![endif]-->', $content);
$content = preg_replace("#<\\?xml[^>]+\\?>\n?#", '', $content);
$content = str_replace(array('/>','xml:lang','application/xhtml+xml'),array('>','lang','text/html'), $content);
// Only replace the doctype in templates with the xml header
if($hasXMLHeader) {
$content = preg_replace('/<!DOCTYPE[^>]+>/', '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">', $content);
}
$content = preg_replace('/<html xmlns="[^"]+"/','<html ', $content);
$response->setBody($content);
}
}
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