PHP Warning: Invalid UTF-8 sequence in argument in /ajax.php on line 24

PHP Warning: Invalid UTF-8 sequence in argument in /ajax.php on line 24

Prior to

      echo json_encode ($result);exit();

should there be something like

      $result = htmlentities((string)$result, ENT_QUOTES, 'utf-8', FALSE); 

Can you describe the steps you took to trigger the error message?

Checkout by credit card (Paypal Express) with this item - the checkout confirmation page is blank in the center column, but the remainder of the page including the footer do render.

The fix I suggested above seems to resolve this issue.

Similar issue identified at: https://www.zen-cart.com/showthread.php?218140-Got-a-blank-page-during-check-out-payment-with-V154

The direction of this thread appeared to resolve the issue.

FWIW, this change breaks one of my commercial plugins. That plugin returns an ***array ***of information to an AJAX request and the suggestion of simply casting the result to a string wrecks havoc!

Here's the change that I made, allowing the return values to be string-value-containing-names or array elements:

<?php
/**
 * ajax front controller
 *
 * @package core
 * @copyright Copyright 2003-2015 Zen Cart Development Team
 * @copyright Portions Copyright 2003 osCommerce
 * @license http://www.zen-cart.com/license/2_0.txt GNU Public License V2.0
 * @version GIT: $Id: Author: Ian Wilson   Modified in v1.6.0 $
 */
require ('includes/application_top.php');

//-bof-lat9  *** 1 of 2 ***
function htmlentities_mixed ($mixed_value, $flags, $encoding = 'utf-8', $double_encode = true) {
  if (!is_array ($mixed_value)) {
    $result = htmlentities ((string)$mixed_value, $flags, $encoding, $double_encode);
    
  } else {
    $result = array ();
    foreach ($mixed_value as $key => $value) {
      $result[$key] = htmlentities_mixed ($value, $flags, $encoding, $double_encode);

    }
  }
  return $result;
  
}
//-eof-lat9  *** 1 of 2 ***

$language_page_directory = DIR_WS_LANGUAGES.$_SESSION['language'].'/';
if (isset ($_GET['act'])&&isset ($_GET['method'])) {
  $className = 'zc'.ucfirst ($_GET['act']);
  $classFile = $className.'.php';
  if (file_exists (DIR_FS_CATALOG.DIR_WS_CLASSES.'ajax/'.$classFile)) {
    require (DIR_FS_CATALOG.DIR_WS_CLASSES.'ajax/'.$classFile);
    $class = new $className ();
    if (method_exists ($class, $_GET['method'])) {
      $result = call_user_func (array(
          $class,
          $_GET['method']
      ));
      
//-bof-lat9  *** 2 of 2 ***
      $result = htmlentities_mixed ($result, ENT_QUOTES, 'utf-8', FALSE);
//-eof-lat9  *** 2 of 2 ***

      echo json_encode ($result);exit();
    } else {
      echo 'method error';
    }
  }
}

lat9:

FWIW, this change breaks one of my commercial plugins....

What is the name of the plugin (so folks who are searching will come to this thread)?

That plugin's name is Products Options Stock Manager (POSM).

Proposed code change slated for v160: https://github.com/zencart/zencart/pull/613
For v1.5.x the code by lat9 should be fine, and only involves touching 1 file.

Thanks, DrByte!

I'm investigating reports of the previously-proposed "fix" being an incomplete, and potentially buggy, approach.

To that end, I'm looking for any information any of you can provide to help me trigger the exact same symptoms with PayPal Pro on v154. Basically looking for details on how to set up a test site with settings to match yours in a way that I can trigger the symptoms ... so I can ensure we come up with as complete a fix as possible.

Feedback welcome ;)