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class.cb_feature_detect.php
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class.cb_feature_detect.php
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<?php
/* This file is part of cbapi.
* Copyright © 2011-2012 stiftung kulturserver.de ggmbh <github@culturebase.org>
*
* cbapi is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* cbapi is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with cbapi. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* MESS. We cannot reliably detect features. Let's admit that.
*/
class CbFeatureDetect {
private $session_name;
private $js;
private $features;
public function __construct($session_name = 'features', $js = 'js')
{
$this->session_name = $session_name;
$this->js = $js;
$this->features = (array_key_exists($session_name, $_SESSION) && is_array($_SESSION[$session_name])) ?
$_SESSION[$session_name] : array();
}
protected function decodeFeatures()
{
foreach ($_POST as $name => $value) {
if ($value === 'true') {
$this->features[$name] = true;
} else if ($value === 'false') {
$this->features[$name] = false;
} else if (is_numeric($value)) {
$this->features[$name] = $value + 0;
} else {
$this->features[$name] = $value;
}
}
}
/**
* Run the feature detection. Preconditions are:
* 1. The current request has no POST parameters.
* 2. We can append ?$js={yes|no} to the current URL and that will constitute
* a valid GET parameter if the feature detection hasn't run yet.
* 3. The session variable $session_name is not currently in use.
* 4. The cookie $session_name is not currently in use.
* 5. No output has been send, yet.
* 6. The GET parameter $js is used to tell the feature detection that it
* cannot rely on cookies and/or JS.
*
* The feature detection run will include a special bit of HTML + Javascript
* and then die(). The Javascript will reload the same page with a POST
* request containing the detected features. It expects to trigger the same
* code path and end up in the run() method again where the features are
* evaluated. After that they're written to $_SESSION[$session_name] and
* returned from the method. The feature detection cookie is set to 'done'
* then so that further calls to this method don't trigger a re-run of the
* detection. Instead $_SESSION[$session_name] is returned.
*
* This means you can run the feature detection without a session, but then
* it will only work once. After that you'll get an empty array. It won't
* usually rerun the detection as the cookie is independent of the session.
*
* However, if no cookies are accepted the feature detection itself is
* incapable of finding out if it has already run. It will however listen to
* the GET parameter $js and avoid running if that is set. The javascript
* code will add a POST parameter "cookies=false" if it can run and detects
* that no $session_name cookie is set.
*
* Obviously we can only detect either absence of JS or absence of Cookies
* with client side code. However, if $js is set to "yes", availability of
* cookies can be determined by checking the presence of the $sesion_name
* cookie. Also, if the Browser is not expected to be able to run JS, the
* cookie is set and then the browser is redirected via HTTP 302. This means
* in the next run of the feature detection we can see if the cookie has been
* set.
*
* You should always conserve the $js GET parameter in further requests if
* it's set to "no". If it's set to "yes" then that's just a way of
* circumventing empty form post actions which lead to browsers doing "weird
* things" (see https://www.w3.org/Bugs/Public/show_bug.cgi?id=14215#c1).
* However, if you want to avoid the 302 redirects in absence of cookies you
* may still want to conserve the $js parameter, even if it's set to "yes".
*/
public static function run($session_name = 'features', $js = 'js')
{
$fd = new CbFeatureDetect($session_name, $js);
return $fd->detect();
}
private function detectBaseFeatures() {
return array(
'cookies' => isset($_COOKIE[$this->session_name]),
'javascript' => !isset($_GET[$this->js]) || $_GET[$this->js] === 'yes'
);
}
public function detect()
{
if ($_COOKIE[$this->session_name] === 'done') {
// don't rerun, even if features haven't been saved
$this->features = array_merge($this->detectBaseFeatures(), $this->features);
$_SESSION[$this->session_name] = $this->features;
return $this->features;
} else if ($_COOKIE[$this->session_name] === 'running' ||
isset($_GET[$this->js]) || !empty($_POST)) {
// some information about features is given in request. Evaluate.
$this->features = $this->detectBaseFeatures();
$this->decodeFeatures();
setcookie($this->session_name, 'done', 0, '/');
$_COOKIE[$this->session_name] = 'done';
$_SESSION[$this->session_name] = $this->features;
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
header('Location: '.$_SERVER['REQUEST_URI']); // obviously submitted by JS
die();
} else {
return $this->features;
}
} else {
// nothing is known, run feature detection if expected to be
// successful.
setcookie($this->session_name, 'running', 0, '/');
require 'lib/framework/3rdparty/browscap/Browscap.php';
$bc = new Browscap('/var/tmp/browscap/');
$browser = $bc->getBrowser();
if ($browser->JavaScript) {
// JS is probably available, try to run FD.
require 'templates/feature_detect.inc.php';
die();
} else {
setcookie($this->session_name, 'done', 0, '/');
$_COOKIE[$this->session_name] = 'done';
$this->features = array(
'javascript' => false,
'cookies' => $browser->Cookies
);
$_SESSION[$this->session_name] = $this->features;
return $this->features;
}
}
}
public function get($feature)
{
return array_key_exists($feature, $this->features) ? $this->features[$feature] : false;
}
public function getAll()
{
return $this->features;
}
}