php防止站外远程提交表单的方法

<?php    
session_start();    
    
if ($_POST['submit'] == "go"){    
    //check token    
    if ($_POST['token'] == $_SESSION['token']){    
        //strip_tags    
        $name = strip_tags($_POST['name']);    
        $name = substr($name,0,40);    
        //clean out any potential hexadecimal characters    
        $name = cleanHex($name);    
        //continue processing....    
    }else{    
        //s all processing! remote form posting attempt!    
    }    
}    
    
$token = md5(uniqid(rand(), true));    
$_SESSION['token']= $token;    
    
 function cleanHex($input){    
    $clean = preg_replace("![\][xX]([A-Fa-f0-9]{1,3})!", "",$input);    
    return $clean;    
}    
?>    
<form action="<?php echo $_SERVER['PHP_SELF'];?>" method="post">    
<p><label for="name">Name</label>    
<input type="text" name="name" id="name" size="20" maxlength="40"/></p>    
<input type="hidden" name="token" value="<?php echo $token;?>"/>    
<p><input type="submit" name="submit" value="go"/></p>    
</form>

if($_POST['vcode'] != get_vcode())
{
    exit('验证码校验失败，无法入库');
}