php转换文件大小为易于阅读的格式

php把文件大小转换成易于阅读的格式，如GB，MB，KB

// A much better and accurate version can be found
// in Aidan's PHP Repository: 
// http://aidanlister.com/repos/v/function.size_readable.php
 
/**
 * Returns a human readable filesize
 *
 * @author      wesman20 (php.net)
 * @author      Jonas John
 * @version     0.3
 * @link        http://www.jonasjohn.de/snippets/php/readable-filesize.htm
 */
function HumanReadableFilesize($size) {
 
    // Adapted from: http://www.php.net/manual/en/function.filesize.php
 
    $mod = 1024;
 
    $units = explode(' ','B KB MB GB TB PB');
    for ($i = 0; $size > $mod; $i++) {
        $size /= $mod;
    }
 
    return round($size, 2) . ' ' . $units[$i];
}
// Example
 
print HumanReadableFilesize(filesize('test_2mb.zip'));
 
// Returns: 
// --> 2 MB