Magento broken after mysql upgrade. Now getting errors in apache error log if anyone can please help

[soy_de_madrid]

Hi after upgrading mysql apache is throwing these error when I visit my Magento 1.9 CE  website (which doesn't load up and is just blank):

[Sun Aug 21 15:25:49.236402 2016] [fcgid:warn] [pid 15353] [client 192.168.0.1:48510] mod_fcgid: stderr: PHP Fatal error:  Uncaught Error: Function name must be a string in /home/public_html/app/code/core/Mage/Core/Model/Layout.php:555
[Sun Aug 21 15:25:49.236434 2016] [fcgid:warn] [pid 15353] [client 192.168.0.1:48510] mod_fcgid: stderr: Stack trace:
[Sun Aug 21 15:25:49.236438 2016] [fcgid:warn] [pid 15353] [client 192.168.0.1:48510] mod_fcgid: stderr: #0 /home/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(390): Mage_Core_Model_Layout->getOutput()
[Sun Aug 21 15:25:49.236441 2016] [fcgid:warn] [pid 15353] [client 192.168.0.1:48510] mod_fcgid: stderr: #1 /home/public_html/app/code/core/Mage/Cms/Helper/Page.php(137): Mage_Core_Controller_Varien_Action->renderLayout()
[Sun Aug 21 15:25:49.236444 2016] [fcgid:warn] [pid 15353] [client 192.168.0.1:48510] mod_fcgid: stderr: #2 /home/public_html/app/code/core/Mage/Cms/Helper/Page.php(52): Mage_Cms_Helper_Page->_renderPage(Object(Mage_Cms_IndexController), 'home')
[Sun Aug 21 15:25:49.236448 2016] [fcgid:warn] [pid 15353] [client 192.168.0.1:48510] mod_fcgid: stderr: #3 /home/public_html/app/code/core/Mage/Cms/controllers/IndexController.php(45): Mage_Cms_Helper_Page->renderPage(Object(Mage_Cms_IndexController), 'home')
[Sun Aug 21 15:25:49.236451 2016] [fcgid:warn] [pid 15353] [client 192.168.0.1:48510] mod_fcgid: stderr: #4 /home/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Cms_IndexController->indexAction()
[Sun Aug 21 15:25:49.236454 2016] [fcgid:warn] [pid 15353] [client 192.168.0.1:48510] mod_fcgid: stderr: #5 /home/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('index')
[Sun Aug 21 15:25:49.236457 2016] [fcgid:warn] [pid 15353] [client 192.168.0.1:48510] mod_fcgid: stderr:  in /home/public_html/app/code/core/Mage/Core/Model/Layout.php on line 555

Any help really appreciated to fix this

[KnowbandPlugins]

Its not recommended to edit the core file. Editing core files causes a lot of problems while updating magento. You should override the file which you have to edit. In this case error can be fixed by fixing following line in magento_root /app\code\core\Mage\Core\Model\Layout.php

$out .= $this->getBlock($callback[0])->$callback[1]();

change it to 

$out .= $this->getBlock($callback[0])->{$callback[1]}();

Reference:- http://www.code007.ro/making-work-magento-with-php-7-rc1/

[soy_de_madrid]

Hi thanks I did the first two steps but wasn't sure what the author means by

"then I had to create the __call magic method to override the parent class’ behavior:"

I tried adding the next couple of steps to the same /Model/Session/Abstract/Varien.php file but I still can't login to the backend. Where should those other changes go?

Thanks again for your help.

[soy_de_madrid]

The other thing I also noticed is if I do the first step and edit the core Layout.php file the site loads up. But if I then revert that change and copy the file to /app/code/local/Mage/Core/Model/Layout.php with the updated change the site still doesn't load up... So how do I also manage to get the override to work?

Thanks again.