Installing Composer and slim, cant get it to work

So this is my first time trying to install and use composer and other packages. I installed composer and slim 3 on my localhost, and it is working just fine.

I then went ahead and installed it with SSH on my remote server. No errors occurred, and all files are there. And in my composer.json file slim is there as well. I have a autoload file.

But when I try to start writing some code, it's like they are not even installed and I get a error like this as an example.

Parse error: syntax error, unexpected '[', expecting ')' in /domainName/public/bootstrap/app.php on line 6.

This is my app.php file

<?php
session_start();

require __DIR__ . '/../vendor/autoload.php';

$app = new \Slim\App([
        'settings' => [
            'displayErrorDetails' => true,
        ]
    ]);

$app->get('/', function($request, $response){
    return 'Home';
});

And this is my index.php file

<?php

namespace App;

require __DIR__ . '/../bootstrap/app.php';

$app->run();

Very basic code to just test and see if it worked, which it does not. After spending many hours on Google I can't find a solution, and all help here will be much appreciated.

As it's working fine locally, but not on the remote server - PHP 5.4 introduced the syntax of square brackets for arrays.

In PHP 5.3 for example, you had to do:

$array = array( 'foo' => 'bar' );

From PHP 5.4 onwards, a short syntax could be used of:

$array = [ 'foo' => 'bar' ];

I'd suggest that the issue you are hitting is that the version of PHP on the server may be an older version than your local pc.