我用Dreamweaver＋PHP做了一个留言板。只有管理员才能修改留言的功能，在Dreamweaver里面可以实现。

现在想实现这个功能：
登录用户和管理员才能修改自己的帖子，而别人尝试修改则会出错，怎么实现呢？

以下是只限管理员才能进入的功能代码：
<?php
if (!isset($_SESSION)) {
session_start();
}
$MM_authorizedUsers = "1";
$MM_donotCheckaccess = "false";

// *** Restrict Access To Page: Grant or deny access to this page
function isAuthorized($strUsers, $strGroups, $UserName, $UserGroup) {
// For security, start by assuming the visitor is NOT authorized.
$isValid = False;

// When a visitor has logged into this site, the Session variable MM_Username set equal to their username.
// Therefore, we know that a user is NOT logged in if that Session variable is blank.
if (!empty($UserName)) {
// Besides being logged in, you may restrict access to only certain users based on an ID established when they login.
// Parse the strings into arrays.
$arrUsers = Explode(",", $strUsers);
$arrGroups = Explode(",", $strGroups);
if (in_array($UserName, $arrUsers)) {
$isValid = true;
}
// Or, you may restrict access to only certain users based on their username.
if (in_array($UserGroup, $arrGroups)) {
$isValid = true;
}
if (($strUsers == "") && false) {
$isValid = true;
}
}
return $isValid;
}
$MM_restrictGoTo = "admin.php";
if (!((isset($_SESSION['MM_Username'])) && (isAuthorized("",$MM_authorizedUsers, $_SESSION['MM_Username'], $_SESSION['MM_UserGroup'])))) {
$MM_qsChar = "?";
$MM_referrer = $_SERVER['PHP_SELF'];
if (strpos($MM_restrictGoTo, "?")) $MM_qsChar = "&";
if (isset($QUERY_STRING) && strlen($QUERY_STRING) > 0)
$MM_referrer .= "?" . $QUERY_STRING;
$MM_restrictGoTo = $MM_restrictGoTo. $MM_qsChar . "accesscheck=" . urlencode($MM_referrer);
header("Location: ". $MM_restrictGoTo);
exit;
}
?>