php-PHP中include后，函数中需要global部分变量

PHP中include后，部分函数中需要global部分变量，例如下面global $db;问，如果不用global，怎么完美解决

/*

• 功能：检测用户登录
• 参数：
• 返回：boolen/function check_login() {if(isset($_SESSION['shell'])==false) return false;* global $db;**$uid = $_SESSION['uid'];$rel = $db->findall('members', "WHERE uid='" . $uid . "'");while ($row = $db->fetch_array($rel)) { foreach ($row as $key => $value) { $uinfo[$key] = $value; }}$ushell = md5($uinfo['password'] . $uinfo['role'] . DSLOG_ENC);if ($ushell == $_SESSION['shell']) { return true;} else { return false;}}?>