callfire webhook gives empty response

I have created Web hook For Outbound resource on event finished

curl -u username:password -H "Content-Type:application/json" -X POST "https://api.callfire.com/v2/webhooks" -d '
{
    "name":"Call sent",
    "resource":"OutboundCall",
    "events":["Finished"], 
    "callback":"here is my call back url and it is https"
}'

webhook is created successfully and i have checked in swagger
and the url is also get hit when oubound call is finished
but issue is that i am getting blank response i should get the below response
{
"timestamp":1469540830377,
"webhookId":3749003,
"webhookName":"Test Webhook",
"resourceType":"OutboundCall",
"events":[
{
"timestamp":1469540830377,
"webhookId":3749003,
"resourceType":"OutboundCall",
"eventType":"Finished",
"resource":{
"id":1024990109003,
"fromNumber":"12132212384",
"toNumber":"12132041238",
"state":"FINISHED",
"campaignId":13194908003,
"batchId":11305143003,
"contact":{
"id":537189974003,
"firstName":"testFirstName",
"lastName":"testLastName",
"zipcode":"90025",
"homePhone":"12132041238",
"workPhone":"12132041238"
},
"inbound":false,
"created":1469565220000,
"modified":1469565232000,
"labels":[
"Test Label 1",
"Test Label 2"
],
"finalCallResult":"AM",
"records":[
{
"id":571797202003,
"billedAmount":1,
"finishTime":1469565233000,
"result":"AM",
"originateTime":1469565225000,
"answerTime":1469565227000,
"duration":6
}
],
"agentCall":false
}
}
]
}

here its doc link https://developers.callfire.com/webhooks-guide.html


Source: stackoverflow-php