PHP Curl with --data flag?

Can someone write a PHP script that reproduces the functionality of this linux shell command?

curl -X POST -u "USERNAME:PASS" \
    -H "Content-Type: application/json" \
        --data '{"aps": {"alert": "this is a message"}}' \
            https://mywebsite.com/push/service/

I think I almost got it in my code, but I'm not sure how to handle the --data attribute.

Here's what my code looks like so far:

    $headers = array();
    $headers[] = "Content-Type: application/json";
    $body = '{"aps":{"alert":"this is a message"}}';

    $ch = curl_init();
    // Set the cURL options
    curl_setopt($ch, CURLOPT_URL,            "https://mywebsite.com/push/service/");
    curl_setopt($ch, CURLOPT_USERPWD,        "USERNAME:PASSWORD");
    curl_setopt($ch, CURLOPT_POST,           TRUE);
    curl_setopt($ch, CURLOPT_POSTFIELDS,     $body);
    curl_setopt($ch, CURLOPT_HTTPHEADER,     $headers);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);

    // Execute post
    $result = curl_exec($ch);

    // Close connection
    curl_close($ch);
    print_r($result);