PHP, display image with Header()

Question

I'm displaying images from outside my web root, like this:

header('Content-type:image/png');
readfile($fullpath);

The content-type: image/png is what confuses me.

Someone else helped me out with this code, but I noticed that not all images are PNG. Many are jpg or gif.
And still they are displayed successfully.

does anyone know why?

question from:https://stackoverflow.com/questions/2633908/php-display-image-with-header

Answer 1

The best solution would be to read in the file, then decide which kind of image it is and send out the appropriate header

$filename = basename($file);
$file_extension = strtolower(substr(strrchr($filename,"."),1));

switch( $file_extension ) {
    case "gif": $ctype="image/gif"; break;
    case "png": $ctype="image/png"; break;
    case "jpeg":
    case "jpg": $ctype="image/jpeg"; break;
    case "svg": $ctype="image/svg+xml"; break;
    default:
}

header('Content-type: ' . $ctype);

(Note: the correct content-type for JPG files is image/jpeg)