xslt php create xml from string

[original]

I've used the following piece of code to transform XML to another XML file. But I'm trying to use xslt to create a new XML file from a set of strings.\[code\] $xsl = simplexml_load_file('template.xsl'); $xslt = new XSLTProcessor; $xslt->setParameter('','foo',$foo); $xslt->setParameter('','bar',$bar); $xslt->setParameter('','test',$test); $xslt->importStyleSheet($xsl); $data = http://stackoverflow.com/questions/14083689/$xslt->transformToXML($xml);\[/code\]So what I'm doing is passing parameters to template.xsl which creates nodes and the resulting output is passed to $data, which PHP then write to a file. But the example code that I have expects a XML file to be read first and saved to a variable, $xml. But I'm not reading in a XML file because I'm generating strings for the data and this generates 'PHP Warning: XSLTProcessor::transformToXml() expects parameter 1 to be object, null given'. I realise that I can use PHP to write the XML - http://www.developerfusion.com/code/3944/how-to-create-xml-files/ - But I would like to know how to do this with xslt.Thanks