Question

What headers should a send with an image output (image.php when opened allows user to download an image) to set caching time for that image to 3 days (instead of re-downloading the image from the user side) ??

and how can i compress the image and send it compressed and what headers should i send along to tell the browser that this image is compressed ?

thank you .

Answer 1

Well, the easiest way to compress is to enabled deflate or gzip from the htaccess level if you’re running apache. If not, you can add the ob_gzhandler() function as the ob_start() callback at the beginning of the document like so:

<?php
if( !ob_start("ob_gzhandler") ) {
    ob_start();
}
//Feel free to echo image data and whatnot, the callback deals with the headers, compatibility, and compression!
?>

Note this requires the zlib extension.

You can also add this function as the ob callback in the php.ini file or enable the zlib.output_compression directive.

As for setting up caching, simply add this header() call before outputting text:

<?php
header('Cache-Control: max-age='.(5184000 * 3).', must-revalidate'); //Cache should last for 3 days
?>