Quix0r,

I was not able to reproduce your problem with a fresh install of the latest stable version of MantisBT (1.2.15 at the moment).

Please provide detailed, step-by-step instructions to reproduce the issue. Additional information listed below may also be useful:

• Exact version of PHP, Database, Web server and Operating System
• Relevant customizations (e.g. changes in config_inc.php, etc)
• Installed plugins or custom functions ?
• Was the MantisBT source code modified in any way ?

Maybe you changed setting $g_display_errors in a not recommended way

To answer your question and requests:

1) php --version:

PHP 5.4.4-14+deb7u2 (cli) (built: Jun 5 2013 07:56:44)
Copyright (c) 1997-2012 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2012 Zend Technologies
with Xdebug v2.2.1, Copyright (c) 2002-2012, by Derick Rethans

mysql --version
mysql Ver 14.14 Distrib 5.5.31, for debian-linux-gnu (x86_64) using readline 6.2

Apache: 2.2.22-13 (according to package manager)

The package 'base-files': 7.1wheezy1

In config_inc.php: (excluding database config, of course)

$g_path = 'http://bugs.my-site.example/';
$g_max_failed_login_count = 3;
$g_administrator_email = 'foo@my-site.example';
$g_webmaster_email = $g_administrator_email;
$g_from_email = 'noreply@my-site.example';
$g_return_path_email = $g_administrator_email;
$g_notify_flags['new']['threshold_min'] = constant('DEVELOPER');
$g_notify_flags['new']['threshold_max'] = constant('DEVELOPER');
$g_notify_flags['new'] = array('bugnotes' => constant('ON'), 'monitor' => constant('ON'));
$g_email_receive_own = constant('ON');
$g_default_language = 'auto';
$g_window_title = 'My Bug-Tracker';
$g_show_footer_menu = constant('ON');
$g_show_project_menu_bar = constant('ON');
$g_status_percentage_legend = constant('ON');
$g_summary_category_include_project = constant('ON');
$g_enable_sponsorship = constant('ON');
$g_sponsorship_currency = '€';
$g_allow_file_upload = constant('ON');
$g_allow_anonymous_login = constant('ON');
$g_anonymous_account = 'anonymous';
$g_show_timer = constant('ON');
$g_show_queries_list = constant('OFF');
$g_display_errors = constant('OFF');
$g_relationship_graph_enable = constant('ON');

$g_password_confirm_hash_magic_string = 'xxxxxxxxxxx';

I have now set the "users" access level to "viewer" and protected it from any changes so that it cannot be used and/or modified.

I have no idea at the moment what is happening.
At line 291 of user_api.php we check that user names can not be empty

# username must consist of at least one character
if( is_blank( $p_username ) ) {
    return false;
}

At line 307 we trigger an error if the user name is invalid
if( !user_is_name_valid( $p_username ) ) {
trigger_error( ERROR_USER_NAME_INVALID, ERROR );
}

I see no way how to register a user without a name.
At least as long you didn't change our error handling, that's why I asked for $g_display_errors

Did you have a look at the error logs of web server, PHP and database?

Do you get other errors when working with MantisBT?
e.g. enter an issue without filling the summary field.
Is it possible?

Did you trim $p_username and $p_email (I presume?) with e.g.:

// Make sure trailing/leading or all-spaces are trimmed away:

$p_username = trim($p_username);

$p_email = trim($p_email);

trim is used in is_blank checking
Why do you ask?

Please answer also my questions.

Ah, okay. :)

I have only set the above variables in config_inc.php, nothing is touched in config_defaults_inc.php. In error logs I only found one:

[Wed Jul 03 xx:xx:xx 2013] [error] [client xxx.xxx.xxx.xxx] File does not exist: /var/www/.../htdocs/http:

I can enter an issue without filling out summery line.

If you need my php.ini (not regular settings) I can upload it here. But then this ticket should be better marked as private.

Check your settings of error_reporting in php.ini
I am quite sure this is causing the problem.

The php.ini says:

error_reporting = E_ALL | E_STRICT | E_DEPRECATED

Add the following line
die ("Detected empty user name");
before line
trigger_error( ERROR_USER_NAME_INVALID, ERROR );
in file user_api.php

Do you get the "Detected ...." message when trying to signup with an empty user name?

Yes, it is being displayed.

I must have been blind and you did not read what I wrote at 0016142:0037385

Maybe you changed setting $g_display_errors in a not recommended way

Probably you did:
$g_display_errors = constant('OFF');

I looked for something like
$g_display_errors = array(
E_WARNING => 'inline',
E_NOTICE => 'none',
E_USER_ERROR => 'halt',
E_USER_WARNING => 'inline',
E_USER_NOTICE => 'none'
);

Remove the line
$g_display_errors = constant('OFF'); in your config_inc.php
and your issue should be fixed.

"The username is invalid. Usernames may only contain Latin letters, numbers, spaces, hyphens, dots, plus signs and underscores."

"A necessary field "Summary" was empty. Please recheck your inputs."