Trying to return associative structs / arrays with XML-invalid keys (e.g. Zend_Db_Profiler_Query) breaks _structValue.

    protected function _structValue($struct, DOMDocument $dom, DOMElement $parent)
    {
        $struct = (array) $struct;

        foreach ($struct as $key => $value) {
          // at this point $struct can have strange keys (.e.g "*_query")
          //  $key=preg_replace('/[^a-zA-Z0-9_-]/','_',$key); // this could sanitize $key
            if ($value === false) {
                $value = 0;
            } elseif ($value === true) {
                $value = 1;
            }

            if (ctype_digit((string) $key)) {
                $key = 'key_' . $key;
            }

            if (is_array($value) || is_object($value)) {
                $element = $dom->createElement($key); // this is generates an exception because $key is invalid XML

Finally, the fault exception handler registered in the constructor fails to output anything because fault() is designed to return the DomDocument Instead. Suggest to register a separate handler.