< ?PHP
/*  * PHP简单利用token防止表单重复提交  */
session_start();
header("Content-Type: text/html;charset=utf-8");
function set_token() {
    $_SESSION['token'] = md5(microtime(true));
}
function valid_token() {
    $return = $_REQUEST['token'] === $_SESSION['token'] ? true: false;
    set_token();
    return $return;
}
//如果token为空则生成一个token 
if(!isset($_SESSION['token']) || $_SESSION['token']=='') {  
    set_token(); 
}    
if(isset($_POST['web'])){  
    if(!valid_token()){  
        echo "token error，请不要重复提交！";  
    }else{  
    echo '成功提交，Value:'.$_POST['web'];  
    } 
}else{ 
?>  
    <form method="post" action="">  
    <input type="hidden" name="token" value="<?PHP echo $_SESSION['token']?>">  
    <input type="text" class="input" name="web" value="www.jb51.net">  
    <input type="submit" class="btn" value="提交" />  
    </form> 
<?PHP 
} 
?>