OneSignal push notification PHP Class

class OneSignal
{
    private $rest_key = 'YOUR_REST_KEY';
    private $app_id = 'YOUR_APP_ID';

    function lunchCURL($fields){
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, "https://onesignal.com/api/v1/notifications");
        curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json',
            'Authorization: Basic '.$this->rest_key));
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
        curl_setopt($ch, CURLOPT_HEADER, FALSE);
        curl_setopt($ch, CURLOPT_POST, TRUE);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $fields);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);

        $response = curl_exec($ch);
        curl_close($ch);

        return $response;
    }

    function sendPushToSingleUser($gcm_id, $notif_title, $notif_text){

        $app_id = $this->app_id;

        $headings = array( // heading = Notification title
            "en" => $notif_title
        );

        $contents = array( // content = Notification text - Alert
            "en" => $notif_text
        );

        $fields = array(
            'app_id' => $app_id,
            'include_player_ids' => [$gcm_id],
            'headings' => $headings,
            'contents' => $contents
        );

        $fields = json_encode($fields);

        return $this->lunchCURL($fields); //CURL
    }

}