- htmlentities: documentation ( source)
<?php
$s = 'subject=90.4.11%20Wissensobjekt%20-%20Virtueller%20Vortrag&body=%0Dhttps%3A%2F%2Fhelpsystem.easylearn.ch%2Fknview.php%3Fuserlang%3Dde%26id%3D20150323161110690-AD28-69E5BEC1%0D';
echo htmlentities($s);