Test if browser supports compression

gzipped-image.php

<?php

if (isset($_GET['i']))
{
    // Send a blank gzipped GIF to test browser capability to decode it
    // See http://www.stevesouders.com/blog/2010/07/12/velocity-forcing-gzip-compression/

    header('Content-Type: image/gif');
    header('Content-Encoding: deflate');
    header('Pragma: no-cache');
    header('Expires: Fri, 01 Jan 2000 00:00:00 GMT');
    header('Cache-Control: no-cache, must-revalidate');
    header('Content-Length: 39');

    echo base64_decode('c/d0s7BMZGRgZGhgYPj//z8DA4PiTxZGIMWgAyJAMgxMTC6MDNYA');
}
else
{
    ?>

    <script>
    a = new Image;
    a.onload = function(){alert(‘OK’);};
    a.onerror = function(){alert(‘KO’);};
    a.src = "<?php echo $_SERVER['REQUEST_URI'] . "?&i=1"; ?>"
    </script>

    <?php
}