title: After extension is removed, if file doesn't exist, send to a particular page
body: <p>My question is somewhat similar to <a href="https://stackoverflow.com/questions/48029681/htaccess-rewrite-to-remove-extension-and-query-string-and-make-into-folder-stru">this one</a> but not exactly and I can't understand it enough to adapt it to my needs.</p>
  <p>I have this htaccess rule to remove file extensions which works well</p>
  <pre><code>RewriteCond %{REQUEST_FILENAME} !-f
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteRule ^([^\.]+)$ $1.php [NC,L]
  </code></pre>
  <p>So <code>/somepage</code> refers to <code>/somepage.php</code>. I now need a sort of fallback to it incase <code>somepage.php</code> doesn't exist.</p>
  <p>In which case <code>/somepage</code> would rewrite to <code>/catchall.php?link=somepage</code> which can handle the requests. How can I do this?</p>