How to zip a whole folder using PHP

I have found here at stackoveflow some code on how to ZIP a specific file, but how about a specific folder?

Folder/
  index.html
  picture.jpg
  important.txt

inside in My Folder, there are files. after zipping the My Folder, i also want to delete the whole content of the folder except important.txt.

Found this here at stack

Zip a whole folder:

// Remove any trailing slashes from the path
$rootPath = rtrim($rootPath, '\\/');

// Get real path for our folder
$rootPath = realpath('folder-to-zip');

// Initialize archive object
$zip = new ZipArchive();
$zip->open('file.zip', ZipArchive::CREATE | ZipArchive::OVERWRITE);

// Create recursive directory iterator
/** @var SplFileInfo[] $files */
$files = new RecursiveIteratorIterator(
    new RecursiveDirectoryIterator($rootPath),
    RecursiveIteratorIterator::LEAVES_ONLY
);

foreach ($files as $file)
{
    // Skip directories (they would be added automatically)
    if (!$file->isDir())
    {
        // Get real and relative path for current file
        $filePath = $file->getRealPath();
        $relativePath = substr($filePath, strlen($rootPath) + 1);

        // Add current file to archive
        $zip->addFile($filePath, $relativePath);
    }
}

// Zip archive will be created only after closing object
$zip->close();

Zip a whole folder + delete all files except "important.txt":

// Remove any trailing slashes from the path
$rootPath = rtrim($rootPath, '\\/');

// Get real path for our folder
$rootPath = realpath('folder-to-zip');

// Initialize archive object
$zip = new ZipArchive();
$zip->open('file.zip', ZipArchive::CREATE | ZipArchive::OVERWRITE);

// Initialize empty "delete list"
$filesToDelete = array();

// Create recursive directory iterator
/** @var SplFileInfo[] $files */
$files = new RecursiveIteratorIterator(
    new RecursiveDirectoryIterator($rootPath),
    RecursiveIteratorIterator::LEAVES_ONLY
);

foreach ($files as $file)
{
    // Skip directories (they would be added automatically)
    if (!$file->isDir())
    {
        // Get real and relative path for current file
        $filePath = $file->getRealPath();
        $relativePath = substr($filePath, strlen($rootPath) + 1);

        // Add current file to archive
        $zip->addFile($filePath, $relativePath);

        // Add current file to "delete list"
        // delete it later cause ZipArchive create archive only after calling close function and ZipArchive lock files until archive created)
        if ($file->getFilename() != 'important.txt')
        {
            $filesToDelete[] = $filePath;
        }
    }
}

// Zip archive will be created only after closing object
$zip->close();

// Delete all files from "delete list"
foreach ($filesToDelete as $file)
{
    unlink($file);
}