Determine if a page is a result of being redirected from a 404 Not Found code

Question

I would like to display some addition text on a page if its a result of a 404 Not Found code. I'd like to reuse the rest of page somewhere else.

<div>
   <?php
      if(page_is_404_redirect)
      {
         <div>Oh no, I couldn't find what you were looking for.</div>
      }  
   >?
   ...
</div>

I didnt find anything on the $_SERVER variable page that seemed to indicate the error code result. How can I check the error code status?

Answer 1

<?php
$previous = $_SERVER['HTTP_REFERER'];
$headers = @get_headers($previous);
if($headers[0] == 'HTTP/1.1 404 Not Found')
{
echo "Previous page was 404 error";
}
?>