Install Magento 1.9x

1.[client] /var/www/html/panrosa/.htaccess: Invalid command ‘Header’, perhaps misspelled or defined by a module not included in the server configuration

An apache’s module whose’s missing. To install it, run:

a2enmod headers

2. If PHP 7 is used when installing Magento 1.9x
Fatal error: Uncaught Error: Function name must be a string in app/code/core/Mage/Core/Model/Layout.php:555

In “app/code/core/Mage/Core/Model/Layout.php”
Modify: $out .= $this->getBlock($callback[0])->$callback[1]();
To: $out .= $this->getBlock($callback[0])->{$callback[1]}();

3. Install soap
apt-get update
apt-get install php-soap

Enable soap extension 
Edit: /etc/php/7.0/apache2/php.ini

Magento 2

Display errors to display error messages (server error 500 or blank page)
Step 1: Edit greatime/app/bootstrap.php by uncomment:
#ini_set(‘display_errors’, 1);
Add or edit index.php in the root directory
/** added by minda to display error messages in browsers when it displays a blank page */
ini_set(‘display_errors’, 1);

Step 2: Enable display of error details on the browser
Go to /var/www/html/magento2ce/pub/errors
cp local.xml.sample local.xml

Magento – Errors & Solutions