php - How to pass string with serialized JSON instead of JSON object in curl parameters

I am using vdociepher, So I need to pass few parameters to vdociepher url but it is recommended to pass " string with serialized JSON instead of JSON object " So I am passing this as per requirement ,but php showing code error like wrong format or improper way of writing.

CURLOPT_URL => "https://dev.vdocipher.com/api/videos/1234567890/otp",
  
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'licenseRules': json_encode({
      'canPersist' => true,
      'rentalDuration' => 15 * 24 * 3600
    })
  ]),

I above url I am getting php error in below lines:

 CURLOPT_POSTFIELDS => json_encode([
        'licenseRules': json_encode({
          'canPersist' => true,
          'rentalDuration' => 15 * 24 * 3600
        })
      ]),

So what is proper way to write string with serialized json

Solution:

You have some typo errors. json_encode({ should be json_encode([, }) should be ]), and 'licenseRules': should be 'licenseRules' =>.

json_encode([
    'licenseRules' => json_encode([
      'canPersist' => true,
      'rentalDuration' => 15 * 24 * 3600
    ])
]),

But you will have "double encoded" JSON. I think that you should send data like this :

json_encode([
    'licenseRules' => [
          'canPersist' => true,
          'rentalDuration' => 15 * 24 * 3600,
    ]
]),