I have a function that defines a custom field on a post type. Say the field is “subhead”.
When the post is saved, I want to do some validation on the input, and display an error message on the post edit screen if necessary. Something like:
// Handle post updating
function wpse_update_post_custom_values($post_id, $post) {
// Do some checking...
if($_POST['subhead'] != 'value i expect') {
// Add an error here
$errors->add('oops', 'There was an error.');
}
return $errors;
}
add_action('save_post','wpse_update_post_custom_values',1,2);
I’m trying to hook this to the save_post action, but I can’t figure out how to handle errors. There doesn’t appear to be an error object passed into the function, and if i create my own WP_Error obj and return it, it’s not respected by whatever mechanism spits out errors on the post edit page.
I currently have an on-page error message inside my custom meta box, but this is less than ideal–I’d rather have a big, red, up-at-the-top error like WP normally displays.
Any ideas?
UPDATE:
Based on @Denis’ answer, I tried a few different things. Storing errors as a global didn’t work, because WordPress does a redirect during the save_post process, which kills the global before you can display it.
I ended up storing them in a meta field. The problem with this is that you need to clear them out, or they won’t go away when you navigate to another page, so I had to add another function attached to the admin_footer that just clears out the errors.
I wouldn’t have expected that error handling for something so common (updating posts) would be this clunky. Am I missing something obvious or is this the best approach?
// Handle post updating
function wpse_5102_update_post_custom_values($post_id, $post) {
// To keep the errors in
$errors = false;
// Do some validation...
if($_POST['subhead'] != 'value i expect') {
// Add an error here
$errors .= 'whoops...there was an error.';
}
update_option('my_admin_errors', $errors);
return;
}
add_action('save_post','wpse_5102_update_post_custom_values',1,2);
// Display any errors
function wpse_5102_admin_notice_handler() {
$errors = get_option('my_admin_errors');
if($errors) {
echo '<div class="error"><p>' . $errors . '</p></div>';
}
}
add_action( 'admin_notices', 'wpse_5102_admin_notice_handler' );
// Clear any errors
function wpse_5102__clear_errors() {
update_option('my_admin_errors', false);
}
add_action( 'admin_footer', 'wpse_5102_clear_errors' );
Store errors in your class or as a global, possibly in a transient or meta, and display them in admin notices on POST requests. WP does not feature any flash message handler.
