Catching the TMDB genres using php [Json]

I'm using the tmdb API to get some movie information ... I was able to do almost everything I need, what I can not get is the genres of movies > categories ... because the genres are within an object. This way:

I'mnotabletoaccessgenres->nameI'musingthiscodeinphptodecode:

$ch=curl_init();curl_setopt($ch,CURLOPT_SSL_VERIFYPEER,false);curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);curl_setopt($ch,CURLOPT_URL,"https://api.themoviedb.org/3/movie/".$_POST['numerofilme']."?api_key=minhaapiaquia&language=pt-BR&append_to_response=videos");
    $result = curl_exec($ch);
    curl_close($ch);

    $obj = json_decode($result);

    echo $obj->genres;

When I use $obj->genres it apênas returns me a array ... if this code is not functional for what I need, please help me by commenting on how I can get the categories ...