What personal information about website visitor can be collected with PHP and JavaScript?
<p>For example I am thinking about things like this:</p>

<ul>
<li>IP - <code>$_SERVER['REMOTE_ADDR']</code></li>
<li>User Agent - <code>$_SERVER['HTTP_USER_AGENT']</code></li>
<li>Referer - <code>$_SERVER['HTTP_REFERER']</code></li>
<li>Language - <code>$_SERVER['HTTP_ACCEPT_LANGUAGE']</code></li>
<li>Screen resolution <code>JS: screen.height, screen.width</code></li>
<li>Browser Plugins <code>JS: navigator.plugins</code></li>
<li><a href="http://stackoverflow.com/questions/440160/detect-version-of-java-using-javascript">Detect Java Version</a></li>
<li><a href="http://stackoverflow.com/questions/159261/cross-browser-flash-detection-in-javascript">Detect Flash Version</a></li>
<li>Operating system <code>JS: navigator.platform</code></li>
<li>(User GPS Position <code>JS: navigator.geolocation</code>)</li>
<li>...</li>
</ul>

<p>I guess this list is not complete so please help me out. What else can you collect about the visitor? I would like to limit this question to PHP and JavaScript methods only.</p>

<p>Disclaimer: You should only collect data you <em>really</em> need and delete it as soon as possible! </p>
