XML-RPC无法通过PHP中的cURL响应POST请求

Question

I'm having some issues with calling WordPress XML-RPC via cURL in PHP. It's a WordPress.com hosted blog, and the XML-RPC file is located at http://sunseekerblogbook.com/xmlrpc.php.

Starting yesterday (or at least, yesterday was when it was noticed), cURL has been failing with error #52: Empty reply from server.

The code snippet we're using is below:

$ch = curl_init('http://sunseekerblogbook.com/xmlrpc.php');
curl_setopt_array($ch, [
    CURLOPT_HEADER => false,
    CURLOPT_HTTPHEADER => [
        'Content-Type: text/xml'
    ],
    CURLOPT_POSTFIELDS => xmlrpc_encode_request('wp.getPosts', [
        1,
        WP_USERNAME,
        WP_PASSWORD,
        [
            'number' => 15
        ]
    ]),
    CURLOPT_RETURNTRANSFER => true
]);
$ret = curl_exec($ch);
$data = xmlrpc_decode($ret, 'UTF-8');

Using cURL directly however, everything returns exactly as expected:

$output = [];
exec('curl -d "<?xml version=\"1.0\" encoding=\"UTF-8\"?><methodCall><methodName>wp.getPosts</methodName><params><param><value><int>1</int></value></param><param><value><string>' . WP_USERNAME . '</string></value></param><param><value><string>' . WP_PASSWORD . '</string></value></param><param><value><struct><member><name>number</name><value><int>15</int></value></member></struct></value></param></params></methodCall>" sunseekerblogbook.com/xmlrpc.php', $output);
$data = xmlrpc_decode(implode('', $output), 'UTF-8');

We've been successfully able to query WordPress since July 2013, and we're at a dead-end as to why this has happened. It doesn't look like PHP or cURL have been updated/changed recently on the server, but the first code snippet has failed on every server we've tried it on now (with PHP 5.4+).

Using the http://sunseekerblogbook.wordpress.com/xmlrpc.php link gives the same issue.

---

Is there anything missing from the PHP code that would cause this issue? That it's suddenly stopped working over 12 months down the line is what has flummoxed me.

Answer 1

Managed to fix it. Looking at the headers sent by cURL, the only differences were that the cURL command line uses Content-Type: application/x-www-form-urlencoded and that the user agent was set to User-Agent: curl/7.30.0.

The choice of content type didn't affect it, but setting a user agent sorted it! It seems WordPress.com (but not self-hosted WordPress.org sites running the latest v3.9.2) now requires a user agent for XML-RPC requests, though this hasn't been documented anywhere that I can find.