XML_CSSML_ALREADY_EXISTS = -2
XML_CSSML_ERROR = -1
XML_CSSML_INVALID_DATA = -4
XML_CSSML_INVALID_DOCUMENT = -5
XML_CSSML_INVALID_FILE = -6
XML_CSSML_NOT_LOADED = -3
XML_CSSML_OK = 0
void is_a( $object, $class)