function merge_with(&$other) {
$this->flags = array_unique( array_merge( $this->flags, $other->flags ) );
$this->references = array_unique( array_merge( $this->references, $other->references ) );
function merge_with(&$other) {
$this->flags = array_unique( array_merge( $this->flags, $other->flags ) );
$this->references = array_unique( array_merge( $this->references, $other->references ) );