CURL执行返回零而没有错误

Question

我正在尝试执行，但没有任何结果。尽管调用了转储功能。有没有人注意到我做的任何遗漏部分或错误？可能是什么原因？提前谢谢！

在我的备份类中，我执行Curl并将其写入外部文件     

    class Backup {
        private $url;
        private $handler;
        private $file;
        private $timeout;
        private $data;
        private $write;
        private $status;

        private $auth_api;

        public function setAuth($key) {
            $this->auth_api = $key;
        }

        public function __construct($timeout = 5000) {
            $this->timeout = $timeout;
        }

        public function init($url, $dir) {
            $this->file = fopen($dir, "w") or die("cant find file location");
            $this->url = $url;

            $this->handler = curl_init();
            curl_setopt($this->handler, CURLOPT_URL, $this->url);
            curl_setopt($this->handler, CURLOPT_FILE, $this->file);
            curl_setopt($this->handler, CURLOPT_RETURNTRANSFER, true); 
            curl_setopt($this->handler, CURLOPT_CONNECTTIMEOUT, $this->timeout);
            curl_setopt($this->handler, CURLOPT_TIMEOUT, $this->timeout);
            curl_setopt($this->handler, CURLOPT_FAILONERROR, true);
            curl_setopt($this->handler, CURLOPT_SSL_VERIFYPEER, 0); 
            curl_setopt($this->handler, CURLOPT_SSL_VERIFYHOST, 0);         
            curl_setopt($this->handler, CURLOPT_USERPWD, $this->auth_api);
            curl_setopt($this->handler, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
        }

        public function execute() {
            $this->data = curl_exec($this->handler);
            $error = curl_error($this->handler);
            $result = array('header' => '', 'body' => '', 'curl_error' => '','http_code' => '');

            if($error != "") {
                $result['curl_error'] = $error;
                return $result;
            }
            $header_size = curl_getinfo($this->handler, CURLINFO_HEADER_SIZE);
            $result['header'] = curl_getinfo($this->data, 0, $header_size);
            $result['body'] = curl_getinfo($this->data, $header_size);  
            $result['http_code'] = curl_getinfo($this->handler, CURLINFO_HTTP_CODE);
            $result['last_url'] = curl_getinfo($this->handler, CURLINFO_EFFECTIVE_URL);
            return $result;
        }


        public function writeTofile() {
            $this->write = fwrite($this->file, $this->data);
            return $this;
        }

        function dump ($val, $exit = true, $return = false )
        {
            $output = "<pre>" . print_r( $val, true ) . "<pre>";
            if($return) return $output;
            echo $output;
            if($exit) exit;
        }

    }

    $curl = new Backup();

    $curl->setAuth('xxxxxxxx.xxxxxxxxxxxxxxxxxxxx');
    $curl->init('https://app.asana.com/api/1.0/users/me', 'backup/'.date('Ymd').'/me.json');
    $curl->execute();
    $result = $curl->writeTofile();
    $curl->dump($result);
?>