title: Json ajax post returning 403 error
body: <p>I'm passing to my php application a json via ajax post. </p>
  
  <pre><code>function ajax(url, json){
  
      var xmlhttp = new XMLHttpRequest();
      xmlhttp.open("POST", url, true);
      xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
      xmlhttp.timeout = 30000;
      xmlhttp.send(json);
  
  }
  </code></pre>
  
  <p>In my development environment (A.K.A. XAMPP on my own computer) everything works fine, but when I try to run it in my web server I get a 403 error.</p>
  
  <p>I noticed that when I pass any other value, like a simple string or number, I don't get this error. It just happens when I try to post some json, like:</p>
  
  <pre><code>[[],[["6V^1",[],6]],1,"","",""]
  </code></pre>
  
  <p>Any clues of whats is going on and how I can solve this problem?</p>