Generate Unique Filename

public static function uniqueFilename(array $file) : string {
    if(is_array($file) and $file['name'] !== '') {
        $extension = pathinfo($file['name'], PATHINFO_EXTENSION);
        $file_name = uniqid() . '.' . $extension;

        if(file_exists('/path/to/file' . $file_name)) {
            static::uniqueFileName($file);
            return '';
        }

        return $file_name;
    } else {
        throw new \Exception("Invalid file.");
    }
}