title: Does RingCentral fax support Expect: 100-continue header?
body: <p>I'm receiving a 400 error from the fax endpoint using the PHP SDK. </p>
  
  <pre><code>Exception: 400 Bad Request (and additional error happened during JSON parse: \
  Response is not JSON) SDK HTTP Error at \
  https://platform.ringcentral.com/restapi/v1.0/account/~/extension/~/fax
  </code></pre>
  
  <p>We are sending an <code>Expect: 100-continue</code> header. Could this be the issue?</p>
  
  <p>We are running on AWS inside a Linux Docker system as in PHP code, MySQL DB and Apache webserver.</p>