File size format conversion

Convert file bytes B to KB, MB, GB, TB

function format_bytes($size,$r) {
$units = array("B", "KB", "MB", "GB", "TB", "PB", "EB", "ZB ", "YB");
for ($i = 0; $size >= 1024 && $i < 4; $i++) $size /= 1024;
return round($size,$r).$units [$i];
}
//$r is the number of decimal places