WordPress | File size from URL

size_from_url.php

<?php 
// Return a neat file size
function nice_file_size($file_url, $precision = 2) {
    $nice_file_size = null;
    $attachment_id = attachment_url_to_postid($file_url); // Gets ID of file from URL
    $file_path = get_attached_file( $attachment_id ); // Gets path using ID
    if ( is_writable( $file_path ) ) { // Locally an error is thrown due to file not being writable
        $size = filesize( $file_path ); // NB filesize only works with the path to the file NOT a URL
        $base = log($size, 1024);
        $suffixes = array('', 'KB', 'MB', 'GG', 'TB');
        $nice_file_size = round(pow(1024, $base - floor($base)), $precision) .' '. $suffixes[floor($base)];
    }
    return $nice_file_size;
}
?>

<?php
// Example
echo nice_file_size($download_url, 0);
?>

File size from URL

This seems crazily verbose but it should be fairly robust and versatile. The previous version relied on you getting the file ID before passing it into the function. This works using just the file URL, containing the process within the function.

The thing to make note of is; the difference between path and url. They're two different things, and the php filesize function only works if you give it the server path to the file, hence why we use attachment_url_to_postid to convert the URL to a WordPress ID and then get_attached_file to get the path. Seems like we're going round the houses but we're not.

$precision is just the number of decimal places you want the file size to display, it defaults to 2 but can be changed to suit. The example uses 0.

Obviously this will only work with files uploaded through the dashboard.

Hope it helps someone else. Big hugs from Cornwall, UK.

Updated May 2022

I discovered that, when working locally, files are typically unable to be accessed due to permissions. This causes filesize to print an error. I've therefore added a condition if ( is_writable( $file_path ) ) { which ensures the file is accessible before running filesize. Probably not a bad condition to have in place regardless of whether you're working locally or not.