functions.PHP，经测试代码如下：
/**
* 通过Session判断检查用户是否已经登录
*
* @param
* @arrange (512.笔记) jb51.cc
**/
function loggedIn(){
//Session logged is set if the user is logged in
//set it on 1 if the user has successfully logged in
//if it wasn't set create a login form
if(!$_SESSION['loggd']){
echo'<form action="checkLogin.PHP" method="post">
<p>
Username:<br>
<input type="text" name="username">
</p>
<p>
Password:<br>
<input type="password" name="username">
</p>
<p>
<input type="submit" name="submit" value="Log In">
</p>
</form>';
//if session is equal to 1,display
//Welcome,and whaterver their user name is
}else{
echo 'Welcome,'.$_SESSION['username'];
}
}
/*** 来自编程之家 jb51.cc（jb51.cc） ***/
<?PHP
//Start the session
session_start();
//This is a simplified HTML Document
?>
<html>
<head>
<title>My Page</title>
</head>
<body>
<?PHP
//Call the functions file
require_once("functions.PHP");
//Display either the user's name,or the login form
//This can be placed on many pages without having
//to re-write the form everytime,just use this function
logedIn();
?>
</body>
</html>
/*** 来自编程之家 jb51.cc（jb51.cc） ***/