Fatal error: Uncaught Error: Function name must be a string in app/code/core/Mage/Core/Model/Layout.php:555

• zendnwar
• February 24, 2016
• Magento
• 192 Comments

This is because you need to clarify the `$callback` variable will be called as a method (function). The original bit of code was:
(file app/code/core/Mage/Core/Model/Layout.php)

Now you need to replace it with this
with:
1 $out .= $this->getBlock($callback[0])->{$callback[1]}();

Don’t edit the files directly – instead create a separate extension which overrides Mage_Core_Model_Layout with your own model. If that isn’t to taste, try creating a new directory:
1 app/code/local/Mage/Core/Model/

Copy Layout.php there, making the necessary changes. You’ll need to clear the cache after any edits. This should mean you can now load your Magento pages.