Untitled

<?php
    require 'vendor/autoload.php';
    session_start();
?>
<!DOCTYPE>
<html>
    <head>
	<meta charset="utf-8"/>
	<title>Curl - YouTube</title>
	<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/semantic-ui/2.1.8/semantic.css"/>
    </head>
    <body>
	<?php
	    $token = NULL;
	    If(isset($_GET['page'])){
		$token = '&pageToken='.$_GET['page'];
	    }

	    $url = 'https://www.googleapis.com/youtube/v3/search?key=AIzaSyCppjkN82gtVLYZHeyVCZ6JnCMAuPrIWIk&channelId=UCdVSf61ldPOWji-SYDCeXeQ&part=snippet,id&order=date&maxResults=10'.$token;
	    $curl = curl_init($url);
	    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, FALSE);
	    curl_setopt($curl, CURLOPT_RETURNTRANSFER, TRUE);
	    $retorno = json_decode(trim(curl_exec($curl)));
	    curl_close($curl);
	    If(isset($retorno->{'nextPageToken'})){
		$_SESSION['next'] = $retorno->{'nextPageToken'};
	    }
	    if(isset($retorno->{'prevPageToken'})){
		$_SESSION['prev'] = $retorno->{'prevPageToken'};
	    }
	    $posterior = $_SESSION['next'];
	    $anterior = $_SESSION['prev'];
	    dump($retorno);
	?>
	<div class="ui six column doubling stackable grid container">
	    <?php foreach ($retorno->{'items'} as $ret): ?>
		<div class="column">
		    <p><img src="<?php echo $ret->{'snippet'}->{'thumbnails'}->{'default'}->{'url'}?>"/></p>
		    <!--Esta é a linha do erro-->
		    <p><a href="video.php?id=<?php echo $ret->{'id'}->{'videoId'}; ?>"><?php echo $ret->{'snippet'}->{'title'}; ?></a></p>
		    <!---->
		</div>
	    <?php endforeach; ?>
	</div>

	<div style="text-align: center">
	    <div class="ui pagination menu">
		<a class="item" href="?page=<?php echo $anterior;?>">Anterior</a>
		<a class="item" href="?page=<?php echo $posterior;?>">Posterior</a>
	    </div>
	</div>
    </body>
</html>