title: php form post content 403 error
body: <p>It was recently brought to my attention by a user on my site that if they submitted this content on any form on my site, they are returned with a 403 error.</p>
  
  <pre><code>make a &lt;hr&gt; add this css to it hr{border:none; border-top:1px solid #000; background:none; height:1px; width:yourwidth;}
  </code></pre>
  
  <p>Here's the background of the form processing (it's not the actual code used on the site).</p>
  
  <pre><code>&lt;?php
  
  
  if (isset($_POST['test'])) {
  
  echo htmlspecialchars($_POST['content']);
  
  }
  
  ?&gt;
  
  &lt;form action = "" method = "post"&gt;
  
  &lt;textarea name = "content"&gt;&lt;/textarea&gt;
  &lt;input type = "submit" name = "test"/&gt;
  
  &lt;/form&gt;
  </code></pre>
  
  <p>It all works fine, as long as the text above isn't submitted into the form. </p>
  
  <p>I try changing the htmlspecialchars to htmlentities, strip_tags anything I could think of really but it still returns a 403 error. How can I prevent this 403 error?</p>