这段代码如何正常工作？

What does this code do ? I can't understand the while loop mainly ! mainly can't understand $total--

function getNiceFileSize($file, $digits = 2)
{
    if(is_file($file)){
        $filePath = $file;
        if(!realpath($filePath)){
            $filePath = $_SERVER["DOCUMENT_ROOT"] . $filePath;
        }
        $fileSize = filesize($filePath);
        $sizes = array("TB", "GB", "MB", "KB", "B");
        $total = count($sizes);
        while ($total-- && $fileSize > 1024){
            $fileSize /= 1024;
        }
        return round($fileSize, $digits). " " . $sizes[$total];
    }
    return false;
}

$total-- is the same as $total -= 1, which is the same as $total = $total -1. This is known as the decrement operator. You are probably familiar with the increment operator when looking at for loops, such as for ($i = 0, $i++, $i < 10).

The loop can be rewritten as while ($total = $total -1 && $fileSize > 1024), which means "while $total is still a truthy value (in this case, a number > 0) and $fileSize is > 1024".