PHP script to convert .gz-compressed files to .bzip2 utilising the system's existing `gunzip` and `bzip2` commands

gz2bz2.php

<?php

/**
 * Fixes PHP's $argv array (or, rather, a list of filenames that is assumed to
 *  come from $argv) to expand glob strings on Windows, where the cmd.exe shell
 *  doesn't expand globs before passing arguments to called commands/programs.
 *
 * @link https://gist.github.com/aziraphale/edf8a1b1ad049f4e08ee
 * @param array $argv
 * @return array
 */
function windowsFixGlobArgv(array $argv)
{
    // Intentionally avoid overwriting the passed array just in case we want
    //  to leave it untouched for other purposes
    $out = [];
    foreach ($argv as $v) {
        if (($v[0] !== "'" && substr($v, -1) !== "'") && strlen($v) !== strcspn($v, '*?{}[]')) {
            // String contains glob-style metacharacters and isn't single-quoted
            $matches = glob($v, GLOB_NOSORT | GLOB_NOCHECK | GLOB_BRACE);
            if ($matches && is_array($matches)) {
                foreach ($matches as $match) {
                    $out[] = $match;
                }
                continue;
            }
        }

        $out[] = $v;
    }

    return $out;
}

$files = array_slice($argv, 1);

if (stripos(PHP_OS, 'WIN') !== false) {
    $files = windowsFixGlobArgv($files);
}

// @todo Ensure existence of `gunzip` and `bzip2` commands
// @todo Option for deleting gzipped files
// @todo Dry-run option (implies verbose on)
// @todo Verbose option

// ## DEFAULT OPTIONS ##
$deleteInputs = false;
$dryRun = false;
$verbose = false;
$continueOnErrors = false;
$continueOnInitialErrors = false;
$continueOnRuntimeErrors = false;

// ## CHANGE OPTIONS HERE FOR DEV ##
//$dryRun = true;
$verbose = true;
//$deleteInputs = true;

$outputNames = [];
foreach ($files as $f) {
    try {
        if (!file_exists($f)) {
            throw new \RuntimeException("File `$f` does not exist.");
        }
        if (!is_file($f)) {
            throw new \RuntimeException("File `$f` is not a 'file'.");
        }
        if (!is_readable($f)) {
            throw new \RuntimeException("File `$f` is not readable.");
        }
        if (!preg_match('/\.(gz|tgz)$/iS', $f)) {
            // @todo Better test here...
            throw new \RuntimeException("File `$f` is not a gzipped file!");
        }

        $outName = $f;
        $outName = preg_replace('/\.gz$/iS', '.bz2', $outName);
        $outName = preg_replace('/\.tgz$/iS', '.tar.bz2', $outName);

        if (file_exists($outName)) {
            throw new \RuntimeException("Output file `$outName` already exists!");
        }

        $outputNames[$f] = $outName;
    } catch (\Exception $ex) {
        if ($continueOnErrors || $continueOnInitialErrors) {
            echo "ERROR: {$ex->getMessage()}\r\n";
        } else {
            throw $ex;
        }
    }
}

foreach ($files as $f) {
    try {
        $in = $f;
        $out = $outputNames[$f];

        $cmd = sprintf(
            'gunzip -c %s | bzip2 > %s',
            escapeshellarg($in),
            escapeshellarg($out)
        );

        if ($verbose) {
            if ($dryRun) {
                echo "Executing [Dry Run]: $cmd ... ";
            } else {
                echo "Executing: $cmd ... ";
            }
        }
        if (!$dryRun) {
            passthru($cmd, $cmdResult);
            $cmdResult = 0;

            if ($cmdResult === 0) {
                if ($verbose) {
                    echo "Complete!\r\n";
                }

                if ($deleteInputs) {
                    if (unlink($in)) {
                        if ($verbose) {
                            echo "Deleted `$in`.\r\n";
                        }
                    } else {
                        throw new \RuntimeException("Failed to delete input file `$in`!");
                    }
                }
            } else {
                echo "\r\n";
                throw new \RuntimeException("Recompression failed for file `$in` => `$out`.");
            }
        }
    } catch (\Exception $ex) {
        if ($continueOnErrors || $continueOnRuntimeErrors) {
            echo "ERROR: {$ex->getMessage()}\r\n";
        } else {
            throw $ex;
        }
    }
}

if ($verbose) {
    echo "\r\nAll finished!\r\n";
}