This PHP Script will decode a base64-encoded file to a separate file, command: php b64_decoder.php filename

b64_decoder.php

<?php

$targetPath=__DIR__."/".$argv[1];
echo $targetPath;
$data = file_get_contents($targetPath);
$content= base64_decode($data);
$file = fopen($targetPath.".decoded", 'w');    
fwrite($file, $content);
fclose($file);
echo "done";