PHP Create Zip file

$exportfname = date("Ymd")."_myfilename.txt";
$exportzname = str_replace(".txt", ".zip", $exportfname);
 
if (file_exists($exportzname))
    unlink($exportzname);
 
$zip = new ZipArchive();
$filename = "./$exportzname";
if ($zip->open($filename, ZIPARCHIVE::CREATE)!==TRUE)
    die("cannot open $filename\n");
$zip->addFile("./$exportfname","/$exportfname");
$z_n = $zip->numFiles;
$z_s = $zip->status;
$zip->close();
 
echo "* numfiles: " . $z_n .  "\n";
echo "* status:" . $z_s .  "\n";