How do I only allow one POST per browser session?

问题

How do I only allow one POST per browser session?

回答1:

<?php
session_start();

if (isset($_SESSION['already_posted'])) {
  echo "Already posted.";
  exit();
}

$is_valid_post = isset($_POST['txt_udid']); // && validate stuff...;

//... process $_POST....

if ($is_valid_post) {
    $_SESSION['already_posted'] = 1;
}

回答2:

save information into $_SESSION after handling submission, and at the beginning of handling submission check if any information were previously saved in $_SESSION.

来源：https://stackoverflow.com/questions/12100521/how-do-i-only-allow-one-post-per-browser-session