Installing Slim, PHP, Ubuntu - php

Question

I'm trying to install Slim on my local LAMP server on Ubuntu only I get stuck at second base.
From my tutorial and various documentation found online:
You now have access to the composer command. Sure enough if I go to
the terminal and enter:
$ composer
Composer version b474944155429eb4cce186c746d55287ee6bb3f4
Usage:
[options] command [arguments]
The next step is to specify Slim as a required package for your app.
This can be accomplished, via a composer.json file within the root of
your project.
Where is the root of my project? I thought it would be
/var/www/slim
I've tried adding composer.json to:
/var/www/slim
and stood in /slim define an index.php script with:
<?php
require 'vendor/autoload.php';
$app = new \Slim\Slim();
$app->get('/hello/:name', function ($name) {
echo "Hello, $name";
});
?>
Go to
http://localhost/var/www/slim
and the browser returns:
Warning: require(vendor/autoload.php): failed to open stream: No such file or directory in /var/www/slim/index.php on line 2
Fatal error: require(): Failed opening required 'vendor/autoload.php' (include_path='.:/usr/share/php:/usr/share/pear') in /var/www/slim/index.php on line 2

Answer 1

Well, there seems to be more then one question in your post, but regardless ...
"Where is the root of my project?"
The root of your project should be in /var/www if you haven't changed your hosts / Apache settings.
Then on to your 2nd question, which I will take the liberty to rephrase :)
"How to create your web App, and include the composer-installed packages inside?"
go to your respective web-root directory, likely in your case /var/www and in it create "index.php". Then, there, in the console, run the command:
composer install
This should install the packages defined in your composer.json, which should in the same web root dir.
If everything went OO, you will have in the following a new directory: /var/www/vendor
Now, go to your web-root directory and create your index.php and in it, in the beginning add the following lines:
require 'vendor/autoload.php';
// to load all the packages installed with composer, not only slim. If
//composer was run in the right directory and w/o problems of course :)
$app = new \Slim\Slim();
// to instantiate Slim script instance and assign it to the pointer $app
$app->get('/hello/:name', function ($name) {
echo "Hello, $name";
})
//to create your 1st route ...

Answer 2

you need to run
composer install
from terminal. After that, add
$app->run();
in index.php.