Notice: Undefined index: file in...

// must be in UTF-8 or `basename` doesn't work
setlocale(LC_ALL,'nl_NL.UTF-8');
$tmp = realpath($_REQUEST['file']);
if($tmp === false)
	err(404,'File or Directory Not Found');
if(substr($tmp, 0,strlen(__DIR__)) !== __DIR__)
	err(403,"Forbidden");

if(!$_COOKIE['_sfm_xsrf'])
	setcookie('_sfm_xsrf',bin2hex(openssl_random_pseudo_bytes(16)));
if($_POST) {
	if($_COOKIE['_sfm_xsrf'] !== $_POST['xsrf'] || !$_POST['xsrf'])
		err(403,"XSRF Failure");
}

$file = $_REQUEST['file'] ?: '.';
if($_GET['do'] == 'list') {
	if (is_dir($file)) {
		$directory = $file;
		$result = array();
		$files = array_diff(scandir($directory), array('.','..'));
	    foreach($files as $entry) if($entry !== basename(__FILE__)) {
    		$i = $directory . '/' . $entry;
	    	$stat = stat($i);
	        $result[] = array(
	        	'mtime' => $stat['mtime'],
	        	'size' => $stat['size'],
	        	'name' => basename($i),
	        	'path' => preg_replace('@^\./@', '', $i),
	        	'is_dir' => is_dir($i),
	        	'is_deleteable' => (!is_dir($i) && is_writable($directory)) || 
	        					   (is_dir($i) && is_writable($directory) && is_recursively_deleteable($i)),
	        	'is_readable' => is_readable($i),
	        	'is_writable' => is_writable($i),
	        	'is_executable' => is_executable($i),
	        );
	    }
	} else {
		err(412,"Not a Directory");
	}
	echo json_encode(array('success' => true, 'is_writable' => is_writable($file), 'results' =>$result));
	exit;
} elseif ($_POST['do'] == 'delete') {
	rmrf($file);