curl_exec尝试连接到URL时返回false

我正在尝试创建一个推送通知应用程序，该应用程序将从服务器向用户设备发送消息。

现在我得到注册ID，但是当我运行curl_exec函数时，出现以下错误：

Curl failed: couldn't connect to host

我不知道为什么，我进行了一些检查，当我尝试将URL更改为“ google.com”时通过了。从我的浏览器中，如果我尝试到达原始URL，则将其重定向到：“ https://developers.google.com/cloud-messaging/ ”这是php代码：

    <?php
class GCM {

    function __construct() {

    }
    /**
     * Sending Push Notification
     */
    public function send_notification($registatoin_ids, $message) {
        // include config
        include_once 'connection.php';

        // Set POST variables
        $url = 'https://android.googleapis.com/gcm/send';

        $fields = array(
            'registration_ids' => $registatoin_ids,
            'data' => $message,
        );

        $headers = array(
            'Authorization: key=' .GOOGLE_API_KEY,
            'Content-Type: application/json'
        );
        // Open connection
        $ch = curl_init();

        // Set the url, number of POST vars, POST data
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4 );
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

        // Disabling SSL Certificate support temporarly
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);

        curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($fields));

        // Execute post
        $result = curl_exec($ch);
        if ($result === FALSE) {
            die('Curl failed: ' . curl_error($ch));
        }

        // Close connection
        curl_close($ch);
        echo $result;
    }
}
?>