如何将URL字符串放在json Viber API php中

I am a newbie developer trying to learn web development. I am currently working on this project where articles from a website get shared automatically to a viber public chat. I am facing this problem where I cannot put the URL in the media. I think this is because its json. I am not sure what I am doing wrong here. I have included.

<?php

$Tid = "-1";
if (isset($_GET['id'])) {
  $Tid = $_GET['id'];
}

$url = 'https://chatapi.viber.com/pa/post';

$jsonData='{
 "auth_token":"4750f56f26a7d2ed-f6b44b76f03d039a-9601b6c9d0d46813",
 "from": "K9/C2Vz12r+afcwZaexiCg==",
 "type":"url",
 "media": "$thisID"
// I want to use $thisID as shown above. But when I
 do so this error appears [ {"status":3,"status_message":"'media' field value is not a valid url."} ] 

// When I use any full form url like https://google.com it works fine 
}';

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $jsonData);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
$result = curl_exec($ch);
curl_close($ch);

?>

This would work as you are using a single quoted literal.

"media": "' . $thisID . '" 

But you are always better to make a PHP array or Object and then use json_encode() to create the JSON String like this

$obj = new stdClass;
$obj->auth_token = "4750f56f26a7d2ed-f6b44b76f03d039a-9601b6c9d0d46813";
$obj->from = "K9/C2Vz12r+afcwZaexiCg==";
$obj->type = 'url';
$obj->media = $thisID;

$jsondata = json_encode($obj);

RESULT of echo $jsondata;

{"auth_token":"4750f56f26a7d2ed-f6b44b76f03d039a-9601b6c9d0d46813",
"from":"K9\/C2Vz12r+afcwZaexiCg==",
"type":"url",
"media":"-1"
}