Not able to get JSON response using CURL PHP - php

Question

I am trying to write a PHP script that post username and password as JSON object to a server and in response get a JSON object that contains UserId and token in JSON.
Following is my code
if (isset($_GET["user"]) && isset($_GET["key"])){
$username = $_GET["user"];
$pass = $_GET["key"];
$data = array("username" => $username, "password" => $pass);
$data_string = json_encode($data);
echo $data_string;
$ch = curl_init('https://sce15.appspot.com/api/g_usrs/signin');
curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
$response = curl_exec($ch);
curl_close($ch);
$usr = json_decode($response, true);
echo $usr;
}
else{
echo "Oops Something went wrong: Error 1";
}
But I am not getting anything in output, my browser window is white blank. I am not able to figure out the mistake. I am able to get JSON object when using javascript for the same URL, but I need to do it with PHP.
Any help is appreciated. Thanks

Answer 1

I finally pointed out the problem after 2 days of head banging on google. It was the SSL certificate error, CURL was not able to verify the SSL certificate.
I got to knew that after checking curl errors print_r(curl_error($ch));
And then by using the curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false); i was able to disable SSL certificate security check. Although it made my connection insecure but i think that's not important in my case.
Thanks Everyone