Creating a post with the REST API, curl and oauth returning 401 error

Question

I'm trying to create a WordPress post using the REST API, OAuth, and cURL. However, I'm running into some trouble.

I'm able to create a blank post (no title, slug, etc) using the following code:

$header = array(buildAuthorizationHeader($oauth), 'Expect:');
$options = array( CURLOPT_HTTPHEADER => $header,
    CURLOPT_ENCODING => "",
    CURLOPT_MAXREDIRS => 10,
    CURLOPT_TIMEOUT => 30,
    CURLOPT_POST => true,
    CURLOPT_URL => $url,
    CURLOPT_CUSTOMREQUEST => "POST",
    CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_SSL_VERIFYPEER => false);

This works as expected - authorizes successfully, and creates a blank post in WordPress. However, when I go to set the title (or any other property) by adding

CURLOPT_POSTFIELDS => "title=testTitle",

I get an error:

{
"data": {
    "code": "json_oauth1_signature_mismatch",
    "message": "OAuth signature does not match",
    "data": {
        "status": 401
    }
},
"headers": [],
"status": 401
}

What's interesting is that I'm able to set a title with success using Postman. Any ideas what I'm doing wrong? Any help would be greatly appreciated - been at this for hours.

Answer 1

"The REST API uses JSON exclusively as the request and response format, including error responses."

-- WordPress REST API Reference

I would try explicitly setting the content type/length and json encode your data with something like this (assuming you need to specify all the options you did in your code provided):

$data = array(
    'title' => 'testTitle',
    'content' => '',
);

$data = json_encode( $data );

$header = array(
    buildAuthorizationHeader( $oauth ),
    'Content-Type: application/json',
    'Content-Length: ' . strlen( $data ),
    'Expect:',
);

$options = array(
    CURLOPT_HTTPHEADER => $header,
    CURLOPT_ENCODING => "",
    CURLOPT_MAXREDIRS => 10,
    CURLOPT_TIMEOUT => 30,
    CURLOPT_POST => true,
    CURLOPT_URL => $url,
    CURLOPT_CUSTOMREQUEST => "POST",
    CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_SSL_VERIFYPEER => false,
    CURLOPT_POSTFIELDS => $data,
);