Question

How do I get the filesize of js file on another website. I am trying to create a monitor to check that a js file exists and that it is more the 0 bytes.

For example on bar.com I would have the following code:

$filename = 'http://www.foo.com/foo.js';
echo $filename . ': ' . filesize($filename) . ' bytes';

Answer 1

You can use a HTTP HEAD request.

<?php
 $url = "http://www.neti.ee/img/neti-logo.gif";
 $head = get_headers($url, 1);
 echo $head['Content-Length'];
?>

Notice: this is not a real HEAD request, but a GET request that PHP parses for its Content-Length. Unfortunately the PHP function name is quite misleading. This might be sufficient for small js files, but use a real HTTP Head request with Curl for bigger file sizes because then the server won’t have to upload the whole file and only send the headers.

For that case, use the code provided by Jakub.