JSON from URL return null : I call a php file from POSTMAN with this url [http://localhost/st/user_login.php?surat=DRIVER&sandi=123]

in user_login.php, i type this to process JSON:
 `$json = file_get_contents('php://input');`
 `$obj = json_decode($json,true);`
 `$email = $obj['surat'];`
 `$password = $obj['sandi'];`

The problem is, $email always return null value.
Can somebody tell me where is the problem?


  [1]: http://localhost/st/user_login.php?surat=DRIVER&sandi=123