www programming

mh ... there is some option that interfere then.
Ok, thank for the report, it will be fixed/checked on next to be sure that it do not happen anymore.

In the while, it is coming the new phpBB extension, which move the integration to the next step.
The plugin with the ext in phpBB installed, is "a perfect world".

The extension will be released improved of "magic things" in next few days, with new 2.4.5, in the while there is this:
https://www.axew3.com/w3/forums/viewtopic.php?p=5194#p5194

Well...
Moving the function just after the call.....
Apparently solved the problem :shock:
I'm not sure how that worked, but it worked. :lol:

 function phpbb_register_url( $register_url ) {
   global $w3all_url_to_cms, $w3all_iframe_phpbb_link_yn, $wp_w3all_forum_folder_wp;
   	
  if( $w3all_iframe_phpbb_link_yn == 1 ){ 
   $wp_w3all_forum_folder_wp = "index.php/" . $wp_w3all_forum_folder_wp;
   $redirect = $wp_w3all_forum_folder_wp . '/?mode=register';
   	return $redirect;
  } else { // register no iframe, direct link to phpBB
     $redirect = $w3all_url_to_cms . '/ucp.php?mode=register';
      return $redirect;
    }

 }

add_filter( 'register_url', 'phpbb_register_url', 10, 1);

Sorry my previous assertion, partially wrong, i should read better before to answer, sorry.
The fact that there is no valid callback, mean that the called function is not found.
[i] function phpbb_register_url( $register_url ) {[/i]
on wp_w3all.php file.
As said, i tested with any plugin configuration and it is working fine, the function is not wrapped inside something that do not let it to be executed.

Did you changed something into wp_w3all.php file?
If not, it is obscure at moment the reason that it do not work in your case.

You could do this to check, or to resolve:

cut the entire function code:
[code] function phpbb_register_url( $register_url ) {
global $w3all_url_to_cms, $w3all_iframe_phpbb_link_yn, $wp_w3all_forum_folder_wp;

if( $w3all_iframe_phpbb_link_yn == 1 ){
$wp_w3all_forum_folder_wp = "index.php/" . $wp_w3all_forum_folder_wp;
$redirect = $wp_w3all_forum_folder_wp . '/?mode=register';
return $redirect;
} else { // register no iframe, direct link to phpBB
$redirect = $w3all_url_to_cms . '/ucp.php?mode=register';
return $redirect;
}

}[/code]
and paste it immediately after the line
[code]add_filter( 'register_url', 'phpbb_register_url', 10, 1);[/code]

I assume it is not a problem that can come out from server, but on how the code is executed.
Very strange.

call_user_func_array() expects parameter 1 to be a valid callback, function 'phpbb_register_url' not found or invalid function name in /home/xxx/public_html/wp-includes/class-wp-hook.php on line 292

Yes, I've enabled the option which redirects registering and lost password to phpbb functions, and I've correctly written the board url in the configuration.
[code]call_user_func_array() expects parameter 1 to be a valid callback, function 'phpbb_register_url' not found or invalid function name in /home/xxx/public_html/wp-includes/class-wp-hook.php on line 292[/code]

I'm using alt-php74, hosted on netsons running on cpanel 92.0.12

So strange, no never reported nor experienced, nor i can reproduce at moment setting any plugin option in any flavor

It is just the function/filter/hook that rewrite wp registration and Lost pass links to point to phpBB instead then wordpress.
I will try to understand how it is possible that it could come out, that seem impossible (to me) at moment...

You want registration and lost pass to point to phpBB and activated this option?

The plugin's URL setting that need to point to phpBB into the plugin admin, i assume is correctly setup? Because the unique reason that it could return a result like this, is that the URL setting is empty.

let see!