Return a file's size in human readable form

human-readable-filesize.php

<?php

/**
 * Return a file's size in human readable form
 * 
 * @param int $bytes File's size in bytes
 * @param int $decimals How many decimals on the returned value
 * 
 * @return string The file's size in human readable form
 */
function human_filesize($bytes, $decimals = 2)
{
    $sz = ['B', 'KB', 'MB', 'GB'];
    $factor = floor((strlen($bytes) - 1) / 3);

    return sprintf("%.{$decimals}f", $bytes / pow(1024, $factor)) . @$sz[$factor];
}