Since version 8.0.0, Bacula-Web dependencies management is performed using Composer.
As stated on Composer's official website,
Composer is a tool for dependency management in PHP. It allows you to declare the libraries your project depends on and it will manage (install/update) them for you.
Let's start by installing Composer on your system
Most Linux distro povides Composer as package, so to install it run this command
On Debian / Ubuntu
$ sudo apt-get install composer
On Red Hat, Centos, Fedora
$ sudo yum install composer
If your distro doesn't provide Composer package, Composer website contains all informations you need to install Composer manually. Please see this page.
From your $HOME folder, run the command below
$ composer create-project --prefer-dist bacula-web/bacula-web bacula-web
Fix files/folders ownership and permissions
On Centos / Red Hat / Fedora
$ sudo mv -v bacula-web /var/www/html/
$ sudo chown -Rv apache: /var/www/html/bacula-web
On Debian / Ubuntu
$ sudo mv -v bacula-web /var/www/
$ sudo chown -Rv www-data: /var/www/bacula-web
$ sudo chmod -Rv 755 /var/www/bacula-web
$ sudo chmod -v 775 /var/www/bacula-web/application/views/cache
$ sudo chmod -v 775 /var/www/bacula-web/application/assets/protected
Note
Depending on your distro, Apache root folder can be /var/www or /var/www/html
Once you're done, it's time to install/configure