Example of modRest, a REST Client, in MODX 2.3.

gistfile1.php

$config = array(
  'baseUrl' => rtrim('http://mywebsite.com/rest/api/','/'),
  'format' => 'json', // json or xml, the format to request 
  'suppressSuffix' => false, // if false, will append .json or .xml to the URI requested
  
  'username' => 'myuser', // if set, will use cURL auth to authenticate user
  'password' => 'mypass',
  'curlOptions' => array(
    'timeout' => 30, // cURL timeout
    'otherCurlOption' => 1,
  ),
  'headers' => array(
    // any HTTP headers to be sent
  ),
  'userAgent' => 'MODX RestClient/1.0.0',
  'defaultParameters' => array(
    'api_key' => 'if i want an api key passed always for every request',
    'other_parameter' => 'these are always sent',
  ),
);
$client = new modRest($modx,$config);

// POST
$result = $client->post('people',array('name' => 'Joe'));
$response = $result->process();
$id = $response['id'];

// PUT
$client->put('people/'.$id,array('name' => 'Joe','email' => '[email protected]'));

$client->get('people',array('id' => $id));

$client->delete('people/'.$id);

Cool, I use it, thank you for nice gist!
One note though: in curlOptions it is better to use CURLOPT_* settings instead of modX aliases as all of those parameters get passed to CURL. It leads to silently failing curl_setopt_array (as it doesn't recognize the option timeout) and the whole CURL request fails with indistinct error message No URL set!.