List the files in the current dir, filtering them by file extension. Like: .zip, .rar, etc.
Modify the variables at the start of the index.php to customize.
$sharedFolder = '/path/to/shared/folder'; //Same folder by default
$allowedFileExtensions = ['rar', 'zip']; //Empty array to allow all
$allowedIps = ['0.0.0.0', '192.168.1.35']; //Empty array to allow everyone