Firstly, we need to install php library for xdebug:

sudo apt update
sudo apt install php7.2-xdebug

For other versions of PHP you can use php7.x-xdebug or php5.x-xdebug for PHP 5.x versions.

Further we need to see /usr/lib/php folder and find our xdebug.so file. 

The main problem of modal windows is different behavior for scrollTop property in iphone and android. So we need to use long list of commands to find scrollTop position. 

Install Apache

sudo apt-get update
sudo apt-get install apache2

Also update settings for apache:

sudo ufw app list
sudo ufw allow in "Apache Full"

You can use /var/www folder for one site, but it will be good to have another folder in your home ~/ directory. So let's add these settings in your apache configs:

sudo nano /etc/apache2/apache2.conf