Json php将数组链接url插入mysql

Question

I can't insert from json -> php -> mysql data

MYSQL datatype: varchar 700 length

What is the problem?

All other data inserts correctly but this I can't add I think because it's a link. It's a problem with $thumbnails = $row['snippet']['thumbnails']['default']['url'];

Json:

"url": "https://yt3.ggpht.com/a-/AN66SAylfIkW5vNxzRmqHzN9GJPJi0CVHOsadKRMPA=s88-mo-c-c0xffffffff-rj-k-no",

Error:

Error : You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ://yt3.ggpht.com/a-/AN66SAylfIkW5vNxzRmqHzN9GJPJi0CVHOsadKRMPA=s88-mo-c-c0xfffff at line 1

code:

$url = 'https://www.googleapis.com/youtube/v3/channels?id=' .implode(',', $allchannels).'&part=snippet%2Cstatistics&key=KEY';

    $content = file_get_contents($url);
    $json = json_decode($content, true);


    foreach($json['items'] as $row)
    {
        $channelid = $row['id'];
        $title = $row['snippet']['title'];
        $description = $row['snippet']['description'];
        $viewCount = $row['statistics']['viewCount'];
        $subscriberCount = $row['statistics']['subscriberCount'];
        $thumbnails = $row['snippet']['thumbnails']['default']['url'];
        $sql = "INSERT INTO users(channelid, title, thumbnails, description, viewCount, subscriberCount) VALUES('$channelid', '$title', $thumbnails, '$description', '$viewCount', '$subscriberCount')  
        ON DUPLICATE KEY UPDATE channelid='$channelid', title='$title', thumbnails='$thumbnails', description='$description', viewCount='$viewCount', subscriberCount='$subscriberCount';
        ";
        mysqli_query($conn, "SET NAMES utf8");
        if(!mysqli_query($conn,$sql))
        {
            die('Error : ' . mysqli_error($conn));
        }
    }