Object of class stdClass could not be converted to string

<?php
    ini_set('display_errors', 1);

    include '../includes/config.php';

    $movie = urlencode($_POST['movie']);

    if($_POST['scelta'] == 'tv' || $_POST['scelta'] == 'movie')
    {
        for($i = 0; $i < 3; $i++)
        {
          $url = "https://api.themoviedb.org/3/search/".$_POST['scelta'].
          "?query=".$movie.
          "&api_key=<<mykey>>&page=".($i+1);

          echo $url ."<br>";

          $output = $class->callApi($url);

          foreach ($output->results as $movie)
          {
            $class->createItemCard($movie, $_POST['scelta']);
          }
        }
    }
?>