Magento 1.x website on PHP7, you need to make some little tweaks in your some Magento 1.x files to make it work without any issues.

1.1 app/code/core/Mage/Core/Model/Layout.php:555

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

With

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