Form resubmission Issue

Question

I have a simple form made that I'm submitting to another php page. The issue that I'm having is that when I get redirected to the new page, if I click refresh, the form gets submitted again. I know that Randy had some type of lesson on this but I can't find the video.

Here's my code where the form is getting created and submitted.

<?php header('Location: index.php'); die(); ?> <body>

<h1>BLOGGING</h1>
<form action="index.php" method="post">
Title: <input type="text" name="title"><br/>
Blog: <textarea rows="10" cols="60" name="post"></textarea><br/><br/>
<input type="submit" style="margin-left: 40%";>
</form>
</body>

Here's my index.php page that is receiving the form and then outputting it.

<div id="main" class="container-fluid"> <h1>My Simple Blog</h1> <div id="blogPosts">  <?php include "includes.php";

if (mysqli_connect_errno()) {
    echo "Failed to connect to the database."; 
}
//escape variables for security reasons
$title = mysqli_real_escape_string($connection, $_POST['title']);
$post = mysqli_real_escape_string($connection, $_POST['post']);

$sql="INSERT INTO blog_posts (title, post) VALUES ('$title', '$post')";

if (!mysqli_query($connection, $sql)){
    die ('Error: ' . mysqli_error($connection));
}
echo "Entry has been recorded.";
mysqli_close($connection);

 $blogPosts = GetBlogPosts();
 foreach ($blogPosts as $post) {
    echo "<div class='post'>";
    echo "<h2>" . $post["title"] . "</h2>";
    echo "<p>" . $post["post"] . "</h1>";
        echo "<span class='footer'>Posted By: " . $post["author_id"] . " Posted On: " . $post["date_posted"] . "</span>";
    echo "</div>";
 }

?>
</div>
  </div>

Answer 1 · 2014-07-16T14:56:02Z

July 16, 2014 2:56pm

I'm not sure I'd want to prevent re-submit. However, if I did, then probably what I'd do is ....

On the originating page, create a hidden field with a randomly generated token:

<input type="hidden" name="form_token" value="9ba8429f096021148c6c81fcb2b3a640" />

Your token generation function looks like this

<?php

function get_form_token() {
  return md5(microtime());
}

?>

Then, on the form processing page, you need to write a couple of functions to Save and Retrieve the form token to see if it's been submitted previously

function save_form_token($token) {
  // code to save token
  // you can write it to file
  // or you can save it to MySQL DB
}

function token_match() {
  // Retrieve all form tokens
  // Loop through all of the to see if you have a match

  foreach ($tokens as $t) {
    if ($t == $token) {
      return TRUE;
    }
  }
  return FALSE;

}
function form_submitted() {
  if ($_SERVER['REQUEST_METHOD'] === 'POST') {
     return TRUE;
  } else {
    return FALSE;
  }
}

$form_token = $_REQUEST['form_token'];

if (form_submitted()) {

 if (token_match()) {
  // Stop processing, this exact form has already been submitted.
   exit;

} 
  save_form_token($form_token);
 // Do your normal form processing here.
}

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daniwao

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Form resubmission Issue

1 Answer

Michael Collins

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