title: Access-Control-Allow-Origin: error in console but file is still uploaded
body: <p>I'm currently learning to code, creating an interactive cognitive experiment in javascript and running it through the survey platform Qualtrics, according to this guide: <a href="https://kywch.github.io/jsPsych-in-Qualtrics/save-php/" rel="nofollow noreferrer">https://kywch.github.io/jsPsych-in-Qualtrics/save-php/</a></p>
  <p>However, the tutorial suggests using the following line of code at the start of my save_data.php file:
  <code>header('Access-Control-Allow-Origin: https://ssd.az1.qualtrics.com')</code>.</p>
  <p>which I noticed in my developer console throws an error. I can get this error to go away by using the correct origin in my php file: <code>header('Access-Control-Allow-Origin: https://universityofsussex.eu.qualtrics.com');</code>.</p>
  <p>However, I've noticed that it doesn't matter what origin I put into the php file, the error will throw if it's wrong, but the file is still successfully stored in the target upload folder. I'm stuck as to what's going wrong here and how to combat this issue - can anyone inform me how to block access from the wrong url origin?</p>
  <p>Thanks</p>