It’s possible to set a callback-function which will be called, if an undefined class should be instantiated during unserializing. (to prevent getting an incomplete object “__PHP_Incomplete_Class”.) Use your php.ini, ini_set() or .htaccess to define ‘unserialize_callback_func’. Everytime an undefined class should be instantiated, it’ll be called. To disable this feature just empty this setting.

A simple fix would be to load the session_start AFTER the object class declaration, but if it is not possible, then you could simply double-serialize the object. Like this:

// some code running in your application
// then,
$_SESSION['myobject'] = serialize($object);

// then when we need it
$object = unserialize($_SESSION['myobject']);

The reason of the error is because the objects stored in sessions are converted to serialized string, and when we call session_start(), it tries to initialize the object with the class definition which isn’t available yet.

$value = date('Y-m-d', mktime(0,0,0,1,$value-1,1900));

The reason why i subtract 1 from the $value because php counts from 1900-01-01, while XLSX has a date from 1900-00-00. So after that conversion we have a valid date.

global $wp_filter;
var_dump($wp_filter['comment_form']);

You will get then something like this:

array(1) {
  [10]=>
  array(2) {
    ["wp_comment_form_unfiltered_html_nonce"]=>
    array(2) {
      ["function"]=>
      string(37) "wp_comment_form_unfiltered_html_nonce"
      ["accepted_args"]=>
      int(1)
    }
    ["akismet_add_comment_nonce"]=>
    array(2) {
      ["function"]=>
      string(25) "akismet_add_comment_nonce"
      ["accepted_args"]=>
      int(1)
    }
  }
}

Pretty cool, now we know what produces all that output.

This was made because Suhosin checks the User-Agent also, and Flash has a different user agent from the browser. Even providing a session id to Flash won’t solve the issue because Suhosin checks the user agents when session_id/session_start is called.

To solve this issue, simply disable user agent encrypting, but leave the IP address encrypting in php.ini:

suhosin.session.encrypt = On
suhosin.session.cryptraddr = On
suhosin.session.cryptua = Off

Well, the fix is pretty simple. While we were setting the From: <email@domain.com> header, now we need to set the Sender header too. So it looks like:

$header='';
$header.="Sender: $from\r\n";
$header.="From: $from\r\n";
$header.="MIME-Version: 1.0\r\n";
$header.="Content-Type: text/html; charset=utf-8\r\n";
$header.="Content-Transfer-Encoding: 8bit\r\n";
 
mail($to, '=?UTF-8?B?'.base64_encode($subject).'?=', $text, $header);

And that’s it. It took me a while googling for the issue to find it, but hopefully it saves your day!