HTTP ERROR 500 - after login to Prestashop admin panel

[Komet]

Hello,

 

I am new to Prestashop and I am trying to get out of this problem with admin panel login.

 

My first installation of Prestashop (still in development stage ver. 1.7.2.2) was made on VPS Centos ver.6.9 - PHP ver. 5.4. For various reasons I had to upgrade to PHP ver. 5.6. I made backup of Prestashop and other sites and made upgrade of PHP. Then restored sites and it looked fine at first - Prestashop frontend showed up. All other sites work fine (Wordpress). Problem is I cannot log in to Prestashop backend. Login page shows but after I enter login/password it shows error:

 

This page isn’t working

... currently unable to handle this request.

 

HTTP ERROR 500:

 

Then I enabled debug mode (changed config/defines.inc.php to enable debug) and got this after enter login/password: 

 

1/1

RuntimeException in classes.php line 118:

Failed to start the session

in classes.php line 118

at NativeSessionStorage->start() in classes.php line 484

at Session->start() in SessionTokenStorage.php line 90

at SessionTokenStorage->hasToken('ANONYMOUS_USER') in CsrfTokenManager.php line 54

at CsrfTokenManager->getToken('ANONYMOUS_USER') in classes.php line 7882

at Router->generate('admin_product_catalog', array()) in Link.php line 722

at LinkCore->getAdminLink('AdminProducts') in AdminController.php line 2018

at AdminControllerCore->getTabs('9', '2') in AdminController.php line 2020

at AdminControllerCore->getTabs('2', '1') in AdminController.php line 2020

at AdminControllerCore->getTabs() in AdminController.php line 1863

at AdminControllerCore->initHeader() in Controller.php line 201

at ControllerCore->run() in Dispatcher.php line 379

at DispatcherCore->dispatch() in index.php line 95

 

Does someone has idea what may be the cause for this error. 
All this happens even when I install fresh demo site. 
I use Installatron for installation.

 

 

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UPDATE: After all it seems it was related to uncomplete PHP update. I have repeated upgrade proces on my VPS and after that Prestashop admin works fine.

Edited September 27, 2017 by Komet (see edit history)