b64_file_decode.php

<?php

    $filePath = @$argv[1];
    $outputExt = @$argv[2];
        
    if (!isset($filePath)) {
        echo "Base64 content file hasn't been actually provided";
        exit; 
    }

    // read content from file and decode it as base64
    $file = file_get_contents($filePath, FILE_TEXT);
    $content = base64_decode($file);
    
    // write output file with same name, assume .html as default extension
    $result = file_put_contents(isset($outputExt) ? $filePath . $outputExt : "$filePath.html", $content, FILE_TEXT);
 
    if (!$result) {
        exit("There was an error in current operation");
    }