用于PHP的Dropbox API正在使用localhost，但不在服务器上

我正在使用Dropbox API for PHP，并开发了一个小应用程序upload and download files from the dropbox .

这在我的本地机器上运行正常（使用WAMP），但如果我在服务器上传它就无法正常工作 .

这是一个错误：

致命错误：未捕获异常'Dropbox \ Exception_NetworkIO'，消息'执行HTTP请求时出错：'在/dropbox-sdk/lib/Dropbox/Curl.php:73

以下是服务器上的cURL设置：

cURL support: enabled
cURL Information: 7.46.0
Age: 3
Features
AsynchDNS: No
Debug: No
GSS-Negotiate: No
IDN: Yes
IPv6: Yes
Largefile: Yes
NTLM: Yes
SPNEGO: No
SSL: Yes
SSPI: No
krb4: No
libz: Yes
CharConv: No
Protocols: dict, file, ftp, ftps, gopher, http, https, imap, imaps, ldap, ldaps, pop3, pop3s, rtsp, scp, sftp, smb, smbs, smtp, smtps, telnet, tftp
Host: x86_64-pc-linux-gnu
SSL Version: OpenSSL/1.0.2e
ZLib Version: 1.2.3.4
libSSH Version: libssh2/1.2.6

我该如何解决这个问题？

编辑：以下是我的代码：

<?php
// Include the Dropbox SDK libraries
require_once "dropbox-sdk/lib/Dropbox/autoload.php";
use \Dropbox as dbx;

// Get access token from dropbox
$appInfo = dbx\AppInfo::loadFromJsonFile("dropbox-sdk/config.json");
$webAuth = new dbx\WebAuthNoRedirect($appInfo, "PHP-Example/1.0");

$authorizeUrl = $webAuth->start();

echo "1. Go to: " . $authorizeUrl . PHP_EOL;
echo "2. Click \"Allow\" (you might have to log in first)." . PHP_EOL;
echo "3. Copy the authorization code." . PHP_EOL;
$authCode = \trim(\readline("Enter the authorization code here: "));

list($accessToken, $dropboxUserId) = $webAuth->finish($authCode);
print "Access Token: " . $accessToken . PHP_EOL;

$dbxClient = new dbx\Client($accessToken, "PHP-Example/1.0");

// Get account info of the user
$accountInfo = $dbxClient->getAccountInfo();
print_r($accountInfo);
?>

编辑：这是堆栈跟踪：

Fatal error: Uncaught exception 'Dropbox\Exception_NetworkIO' with message 'Error executing HTTP request: ' in /dropbox-sdk/lib/Dropbox/Curl.php:73
Stack trace:
#0 /dropbox-sdk/lib/Dropbox/RequestUtil.php(200): Dropbox\Curl->exec()
#1 /dropbox-sdk/lib/Dropbox/WebAuthBase.php(41): Dropbox\RequestUtil::doPostWithSpecificAuth('PHP-Example/1.0', 'Basic d25qZDV0c...', NULL, 'api.dropbox.com', '1/oauth2/token', Array)
#2 /dropbox-sdk/lib/Dropbox/WebAuthNoRedirect.php(80): Dropbox\WebAuthBase->_finish('nNHnBxvAE8qAAAA...', NULL)
#3 /getAccessTokenForDropbox.php(21): Dropbox\WebAuthNoRedirect->finish('nNHnBxvAE8qAAAA...')
#4 {main} thrown in /dropbox-sdk/lib/Dropbox/Curl.php on line 73