Install and setup LAMP stack + Composer on a clean Ubuntu 16.04 VPS

ubuntu-16-vps-lamp.sh

#!/usr/bin/env bash
APACHE_USER=wwwhost
VHOSTS_DOMAINS=(example.com second.example.com)

sudo ufw allow in "OpenSSH"

# Install Apache
sudo apt-get update
sudo apt-get install apache2
sudo nano /etc/apache2/apache2.conf # Add ServerName ... directive at bottom
sudo apache2ctl configtest
sudo systemctl restart apache2
sudo ufw allow in "Apache Full"

# Install MySQL
sudo apt-get install mysql-server
sudo mysql_secure_installation

# Install PHP
sudo apt-get install php libapache2-mod-php php-mcrypt php-mysql
sudo nano /etc/apache2/mods-enabled/dir.conf # Move index.php to start
sudo systemctl restart apache2

# Install Composer
sudo apt-get install curl php-cli git
curl -sS https://getcomposer.org/installer | sudo php -- --install-dir=/usr/local/bin --filename=composer

# Secure Apache
sudo adduser $APACHE_USER
sudo nano /etc/apache2/envvars # Update APACHE_RUN_USER & APACHE_RUN_GROUP to '$APACHE_USER'

# Create VirtualHosts
for $DOMAIN in "${VHOSTS_DOMAINS[@]}"
do
    sudo mkdir -p /var/www/$DOMAIN/public_html
    sudo chown -R $APACHE_USER:$APACHE_USER /var/www/$DOMAIN
then

sudo chmod -R 755 /var/www

for $DOMAIN in "${VHOSTS_DOMAINS[@]}"
do
    sudo cp /etc/apache2/sites-available/000-default.conf /etc/apache2/sites-available/$DOMAIN.conf
    # Edit & enable vhost after copying
    # sudo nano /etc/apache2/sites-available/$DOMAIN.conf
    # sudo a2ensite $DOMAIN.conf
then

sudo a2enmod rewrite
sudo systemctl restart apache2

hello
i tried this on my armbian.
The problem:
how can i load the vendor/autoload file for the composer??

require_once(DIR . '/vendor/autoload.php');

not work
file not found...