$ _POST'值只能使用一次？

Question

post-data.php cantain a form to post user'name into show-post-data.php.
post-data.php

<form method="post" action="show-post-data.php">
user:<input type="text" name="user"></input>
        <input type="submit" name="submit" value="submit">
</form>

Only one command var_dump($_POST);in show-post-data.php

<?php
var_dump($_POST);
?>

1.click 127.0.0.1/post-data.php in browser.
2.input tom and click submit button.
3.click 127.0.0.1/show-post-data.php in browser.
We get output as below:

array(2) { ["user"]=> string(3) "tom" ["submit"]=> string(6) "submit" }

4.click 127.0.0.1/show-post-data.php in browser for second time.

Nothing as output.$_POST is empty now.
$_POST'value can only be used for one time?

Answer 1

This is because of the HTTP protocol is stateless, which means that the information that you send in a request will be only available for that request (unless you store it in the server).

When you send information in a POST, that arrives to the server (to your PHP code) in the variable $_POST, you can use in in that request. In the next page load, that variable will be empty unless you send new information again. That is the correct behavior.