think\File::checkExt PHP Method

    public function checkExt($ext)
    {
        if (is_string($ext)) {
            $ext = explode(',', $ext);
        }
        $extension = strtolower(pathinfo($this->getInfo('name'), PATHINFO_EXTENSION));
        if (!in_array($extension, $ext)) {
            return false;
        }
        return true;
    }