This is not possible because you're mixing client-side behavior with server-side behavior. What you need to do is create an AJAX request to the server.

If you were using a library like jQuery (which you really want to, because it makes AJAX a breeze) you would do something like this:

PHP Code (maybe randomImages.php?)

// query for all images

// $_GET['limit'] will have the limit of images

// since we passed it from the Javascript

// put them all in an array like this:

$images = array('images/20.11.A1B9.jpg','images/20.11.A1B9.jpg',...);

print json_encode($images); // return them to the client in JSON format.

exit;

Client Side Javascript

function getRandomImages(limit) {

    // make request to the server

    $.getJSON('/path/to/randomImages.php', {limit: limit}, function(data) {

        // data is now an array with all the images

        $.each(data, function(i) {

            // do something with each image

            // data[i] will have the image path

        });

    });

}

Alternatively, if the amount of images is finite, you can skip all this crazyness and simply have an array with all the images and generate 8 random ones from the Javascript itself. This would probably be better for smaller data sets and even some bigger ones.