PHP transform xml string to XSLT

I'm trying to run an xslt script over a xml response. But I'm having problems getting PHP/XSLT to understand the response. My PHP looks like this, the $data variable contains the XML

    $movies = new SimpleXMLElement($data);

    // Load the XML source
    $xml = new DOMDocument;
    $xml->load($movies);

    $xsl = new DOMDocument;
    $xsl->load('/var/www/html/app/views/xslt/rdf.xsl');

    // Configure the transformer
    $proc = new XSLTProcessor;
    $proc->importStyleSheet($xsl); // attach the xsl rules

    $res = $proc->transformToXML($xml);

I'm getting

production.ERROR: exception 'ErrorException' with message 'DOMDocument::load(): I/O warning : failed to load external entity "/var/www/public/
"'

as my error. I've tried using simplexml_load_file and simplexml_load_string but have similar results.