如何从一个PHP到另一个PHP获取文本框值

Currently I am working on php project. I tried to bring textbox value, which is

$password = $_POST['password'] 

from Forgotpassword.php to Thank-You.php file.

A lot of people advised me to put include('Forgotpassword.php') on Thank-You.php but when I put include('Forgotpassword.php') on Thank-You.php, whole form from forgotpassword.php was showed on Thank-You.php. I just want to retrieve only textbox value on Forgotpassword.php.

Any idea?

You can done it by using session, in your Forgotpassword.php

<?php
session_start();
$data=$_POST['key'];
$_SESSION["variable"] = $data;
?>

And in your thankyou.php

<?php
session_start();
$data=$_SESSION["variable"];
echo $data;
?>

Forgotpassword.php:

<form method="post" action="Thank-You.php">
    <input type="password" name="password" />
    <input type="submit" value="Submit" />
</form>

Thank-You.php:

<?php $password = $_POST['password'];