I looked at the newer plugin internally and it seems not be setup correctly. Line 44+ of /plugins/alt/lib-auth.php reads:
require_once(dirname(__FILE__) . '/../../zp-core/classes.php'); require_once(dirname(__FILE__) . '/../../plugins/ldapLogon.php');

It probably should be something like:
require_once(dirname(__FILE__) . '/../../zp-core/classes.php'); // root is two level above require_once(dirname(__FILE__) . '/../ldapLogon.php'); // The plugins folder is one level above the /alt folder

Or just try the actual absolute paths:
SERVERPATH . '/'. ZENFOLDER . '/classes.php
SERVERPATH . '/'. USER_PLUGINS_FOLDER . '/ldapLogon.php

(I did not test these changes)

Hello,
I have tried with the actual absolute paths and I could not login I got a white page, so, now I put back the original "/plugins/alt/lib-auth.php"
This "ldapLogon" plugin is not working for me.

Best Regards.

MyAGzenphoto

Then try to contact its developer. Sorry, I cannot help with this plugin.

OK.
I will contact the developer.
Thanks so much.

Best Regards.

MyAGzenphoto

Hello,

Finally, the ldaplogon is seen by zenphoto because of the advices of the delopper. I could configure it but now I have a blank page while using admin.php and I have the following error in the /var/log/apache2/error.log file:

[Tue Oct 31 14:00:19.094032 2017] [:error] [pid 1257] [client 10.1.2.185:51979] PHP Fatal error

Allowed memory size of 134217728 bytes exhausted (tried to allocate 926577468 bytes) in /var
/www/html/zenphoto/zp-core/functions-common.php on line 136

Can you help me or shall I send this info to the developer ?
Best Regards.

MyAGzenphoto

Glad you got it working again. Best the instructions are update on the plugin itself, too. It would probably be useful if the issue tracker on the plugin's repo was enabled.

Since I cannot tell anyhting about that error except what it tells, best ask the plugin developer about it. Especially if it does not appear without the plugin.

OK, I will let it now to the devolopper