Wordpress - Form validation on user profile edit
I worked it out.
add_action( 'user_profile_update_errors', 'validate_steamid_field' );function validate_steamid_field(&$errors, $update = null, &$user = null){ if (!preg_match("/^STEAM_[0-5]:[01]:\d+$/", $_POST['_bbp_steamid'])) { $errors->add('empty_steamid', "<strong>ERROR</strong>: Please Enter a valid SteamID"); }}