3

I have a front-end form posting to admin_post. Here, I do some validation. If there are errors, I want to show an error message for the relevant fields.

However, I don't know how to redirect back to the submission page and retain the field values.

Currently I'm using the below:.

add_action( 'admin_post_form', 'form_post' );
function form_post() {
  $validate = // Validation functions go here
  if ($validate == 'error') {
    $url = wp_get_referer();
    $url = add_query_arg( 'error', 'email', $url );
    wp_redirect( $url );
    die();
  }
}

But this (naturally) doesn't retain the filled form field values, so the user has to start all over again.

If I were posting to the same page as the form this would be simple - just set the value as <input value="<?php echo $_POST['email']; ?>"> but I'm not sure how to achieve the same effect using admin-post.

Can you help?

1
  • PS I could pass the data in the query string and use $_GET but I'd rather not pass sensitive data in the url Dec 14, 2017 at 21:42

3 Answers 3

1

You can use set_transient with the user_id if you are relying on users being logged in, otherwise, cookie would probably be better. For logged in users, you can have the user_id get set within the name of the transient. An example here:

function form_post() {
    $user_info = wp_get_current_user();
    $user_id = $user_info->exists() && !empty($user_info->ID) ? $user_info->ID : 0;
    $url = wp_get_referer();

    // Validate the form fields and populate this array when errors occur
    $validation_errors = array();  // I like to use the id of the elements as keys and the error string as the values of the array, so i can add error class to the elements if needed easily...

    // Now to save the transient...
    if (!empty($validation_errors)) {
        set_transient('validation_errors_' . $user_id, $my_errors);
        wp_redirect($url);
        die();
    }
}

Now before you output your form element on your page, you just need to check the transient for that user, if exists, output the errors, than delete the transient right after that...

For example:

<?php 
$user_info = wp_get_current_user();

$user_id = $user_info->exists() && !empty($user_info->ID) ? $user_info->ID : 0;
$validation_errors = get_transient('validation_errors_' . $user_id);

if ($validation_errors !== FALSE) {
   echo '<div class="errors">Please fix the following Validation Errors:<ul><li>' . implode('</li><li>', $validation_errors) . '</li></ul></div>';
   delete_transient('validation_errors_' . $user_id);
} ?>

<form ...>

</form>
0

I solved this using the $_SESSION variable to pass data to the following page.

  if ($validate == 'error') {
    $_SESSION['formstatus'] = 'error';
    $_SESSION['formdata'] = $_POST;
    $url = wp_get_referer();
    wp_redirect( $url );
    die();
  }

And

<input name="email" value="<?php echo $_SESSION['formdata']['email']">

Finally, clear the data at the bottom of the page, after we've used it...

$_SESSION['formstatus'] = $_SESSION['formdata'] = null;
2
  • In general $_seesion should never be used as it will break on multi server setup and when caching is used. If you want to go that way you should use cookies. Feb 28, 2018 at 15:56
  • Thanks, I wasn't aware of session issues. Looks like cookies is the way to go then. Feb 28, 2018 at 16:26
0

You should just pass all the arguments. This obviously not a great solution when trying to pass them on the URL, so use of cookies might be a much better solution.

But frankly, on a modern web site you should just use AJAX, report and handle the errors on browser side and also redirect from it.

4
  • Thanks, looks like cookies might be the way then. Ajax is great and is my default submission method, but we should always provide a fallback too. Feb 28, 2018 at 16:25
  • @KevinRobinson An alternative fallback in this case can be to submit to the same URL of the page on which the form is and not to use the admin_post end point Feb 28, 2018 at 16:47
  • And if you need to upload files? IE 9 and less doesn't support file upload via ajax. This is my dilemma.
    – Radmation
    Sep 7, 2018 at 20:35
  • Not sure what can you do in that case as you can not repopulate the file field with the file. Some things are just hard to do especially on limited browsers. Sep 8, 2018 at 3:14

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