note 40875 added to function.xslt-process

I have a problem with the xslt_process function: $xslproc = xslt_create(); $varxml = $this->stoDecorationRobot->getXmlByName("banner"); $varxsl = implode("", file("incl_PUI/banner.xsl")); $args = array ("/_xml" => $varxml, "/_xsl" => $varxsl); $argxml = "arg:/_xml"; $argxsl = "arg:/_xsl"; // get the result $result = xslt_process($xslproc, $argxml, $argxsl, NULL, $args); An '&' character in the xml-source ("http://banner.1und1.com/xml/banner?size=3&number=4") occures the following message: Warning: Sablotron error on line 1: XML parser error 4: not well-formed (invalid token) in /home/info/biddysoft.de/incl_PUI/PUI_Stage.php on line 78 What can I do? ---- Manual Page -- http://www.php.net/manual/en/function.xslt-process.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+40875 Delete -- http://master.php.net/manage/user-notes.php?action=delete+40875&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+40875&report=yes Search -- http://master.php.net/manage/user-notes.php