title: PHP, display image with Header()
body: <p>I'm displaying images from outside my web root, like this:</p>
  
  <pre><code>header('Content-type:image/png');
  readfile($fullpath);
  </code></pre>
  
  <p>The content-type: image/png is what confuses me.</p>
  
  <p>Someone else helped me out with this code, but I noticed that not all images are PNG.  Many are jpg or gif.<br>
  And still they are displayed successfully.</p>
  
  <p>does anyone know why?</p>