用于显示图像的PHP脚本很慢

Question

So I have a site that requires login to view, which has a photo gallery. In order to protect those photos I've moved them outside the web root and use a php script to display them. Something like this.

photogallery.php

echo '<img src="photo.php?id=X"/>';

photo.php

$id = (int)$_GET['id'];

$photo = getPhotoDataFromDb($id);
$path  = DIRECTORY.basename($photo['filename']);

// Make sure photo file exists
if (!file_exists($path) || !is_file($path))
{
    logError(__FILE__.' ['.__LINE__.'] No photo found in directory ['.$path.'] for photo id ['.$id.'].');
    header('HTTP/1.0 404 Not Found');
    return;
}

$info = getimagesize($path);

header("Cache-control: public, no-cache;");
header("Content-type: ".$info['mime']);

readfile($path);

Everything works fine except that this is 6 to 7 times slower than just displaying the photos normally from a directory inside the web root.

So, my questions are:

1. Is there something wrong with my code, or does this method always add more time?
2. How can I speed things up? Is there a safe way to cache the images? I believe Gallery 2 does this somehow.

Answer 1

1. Yes your method adds time, by having the image outside of the loop you FORCE PHP to buffer each image into memory, then send it to the user, thereby increasing load on your server and creating a noticeable delay for LARGE images (assuming gallery here).

2. You can speed this up by having your images in the root of your website/app. To protect your images from remote hotlinking, simply use an htaccess script (google for it). You can also create a combination of htaccess and login permissions to keep un-approved users out of the folders containing the images.

References:

• Hotlinking: https://stackoverflow.com/a/1245917/158014
• Issues with readfile() http://php.net/manual/en/function.readfile.php
• Protecting directories with HTACCESS: http://www.bignosebird.com/apache/a10.shtml (this example can be taken further with tying in sessions, logins, etc;)
• PHP and htaccess: Retrieve .htaccess login name from PHP