PHP会话控制实例代码与详细分析

<?php

session_start();

define('u','a');

define('p','1');

if(isset($_GET['r']) &&$_GET['r']== 1) {

  unset($_COOKIE['username']);

  unset($_COOKIE['password']);

  unset($_SESSION['valid_login']);

}

if(isset($_POST['username']) && isset($_POST['password'])) {

  $username=$_POST['username'];

  $password=$_POST['password'];

  if($username== u &&$password== p) {

    $_SESSION['valid_login'] = 1;

    setcookie('username',$username);

    setcookie('password',$password);

  }else{

    echo'incorrect u or p';

  }

}

?>

<?php

if(isset($_SESSION['valid_login'])) {

  printf('welcom, %s',$_COOKIE['username']);

}else{

?>

<form action=""method="post">

  <input type="text"name="username"value=""/>

  <input type="password"name="password"value=""/>

  <input type="submit"/>

</form>

<?php

}

?>

<br />

<a href="cookie_session.php"title="">refresh</a>

<br />

<a href="cookie_session.php?r=1"title="">clear</a>