php zip archive is created but empty

Question

i try to create a zip archive of pdf files like this:

$path = str_replace('\\', '/',WP_CONTENT_DIR . '/uploads/pdf-files');

$zip = new ZipArchive();

$filename = str_replace('\\', '/', WP_CONTENT_DIR . '/uploads/pdf-files/zip-file.zip');

if($zip->open($filename, ZipArchive::CREATE) !== true) {
    die("Error open");
}

if(is_dir($path)) {
    if($dh = opendir($path)) {
        while(($file = readdir($dh)) !== false) {
            $file_parts = pathinfo($file);

            if($file_parts['extension'] == 'pdf') {
                if($zip->addFile($path . '/' . $file) !== true) {
                    die("Error addFile");
                } else {
                    echo $file . "\n";
                }
            }
        }

        closedir($dh);
    }
}

if($zip->close() !== true) {
    die("Error close");
}

echo content_url('uploads/pdf-files/zip-file.zip');

wp_die();

All expected files echo in the else. But the zip archive is empty. Why?

This code should return an url to the zip archive, for download it via javascript.

Answer 1

In found a solution. If i put a second argument (filename) to addFile it works:

$zip->addFile($path . '/' . $file, $file);