random add num prefix to file

rename.php

<?php
$files = scandir('.');
shuffle($files);
$i = 1;
foreach($files as $file){
    if(preg_match('/^\./', $file)){
        continue;
    }
    if(!preg_match('/(mp3|wav)$/', $file)){
        continue;
    }
    $prefix = sprintf("%03d", $i);
    if(preg_match('/__/', $file)){
        rename($file, preg_replace('/^.*__/', $prefix.'__', $file));
    }else{
        rename($file, $prefix.'__'.$file);
    }
    $i++;
}