Shopify词法错误：json文本中的char无效

I am using the shopify PHP client of "cmcdonaldca" - https://github.com/cmcdonaldca/ohShopify.php

On creating a webhook it gives the lexical error in response.here is the code.

$sc = new ShopifyClient($_SESSION['shop'], $_SESSION['token'], $api_key, $secret);

$b = '{"webhook":{"topic":"orders/create","address":"http://www.abc.com","format": "json"}}';

try 
{
       $webhooks = $sc->call('POST','/admin/webhooks.json',$b);
}
catch (ShopifyApiException $e)
{
    var_dump($e->getResponse());
}

All you need to do is because i am POSTing the request in JSON format.what shopify library do after reading the path is, convert the request into json by

"json_encode($params);"

and to rearrange the slashes finally

stripslashes(json_encode($params));"

because our request is in json,so we dnt need to encode it again and if we do so it gives the error.

simply omit the 'json_encode' and 'stripslashes' in 'shopify.php',and here we go.