Magento 2 console command run from an adminhtml page generates an error -- why?

Question

I'm trying to run a Magento 2 console command from within an adminhtml Controller in a custom module. (The module itself is configured correctly, enabled, and running just fine with no errors.)

I figured I'd give one of the built-in commands a shot to ensure it works properly before attempting my own custom command.

When triggered via a cron job, it runs with no errors:

php-cli /home/[sharedHostingName]/public_html/bin/magento --list > /home/[sharedHostingName]/public_html/var/log/test.log

But if I trigger it from my adminhtml Controller, I get an error part-way through the output:

We're sorry, an error occurred. Try clearing the cache and code generation directories. By default, they are: var/cache, var/di, var/generation, and var/page_cache.

I've tried clearing all four of those directories several times with no luck. I get the same result each time.

What am I doing wrong?

Here's my Controller:

<?php

namespace [CompanyName]\Module\Controller\Adminhtml\Test;

class Index extends \Magento\Backend\App\Action
{

    protected $jsonResultFactory;
    protected $context;
    private $resultData;

    public function __construct(
        \Magento\Backend\App\Action\Context $context,
        \Magento\Framework\Controller\Result\JsonFactory $jsonResultFactory
    ) {

        $this->jsonResultFactory = $jsonResultFactory;
        return parent::__construct($context);

    }

    public function execute()
    {

        $result = $this->jsonResultFactory->create();

        system('php-cli bin/magento --list > /home/[sharedHostingName]/public_html/var/log/test.log');

        $this->resultData["message"] = "test AJAX response";
        $result->setData($this->resultData);
        return $result;

    }

    protected function _isAllowed()
    {
        return $this->_authorization->isAllowed('ACL RULE HERE');
    }            

}

...And here's the full output written to the log (error at bottom):

Magento CLI version 2.1.2

Usage:
 command [options] [arguments]

Options:
 --help (-h)           Display this help message
 --quiet (-q)          Do not output any message
 --verbose (-v|vv|vvv) Increase the verbosity of messages: 1 for normal output, 2 for more verbose output and 3 for debug
 --version (-V)        Display this application version
 --ansi                Force ANSI output
 --no-ansi             Disable ANSI output
 --no-interaction (-n) Do not ask any interactive question

Available commands:
 help                                      Displays help for a command
 list                                      Lists commands
admin
 admin:user:create                         Creates an administrator
i18n
 i18n:collect-phrases                      Discovers phrases in the codebase
 i18n:pack                                 Saves language package
info
 info:adminuri                             Displays the Magento Admin URI
 info:backups:list                         Prints list of available backup files
 info:currency:list                        Displays the list of available currencies
 info:dependencies:show-framework          Shows number of dependencies on Magento framework
 info:dependencies:show-modules            Shows number of dependencies between modules
 info:dependencies:show-modules-circular   Shows number of circular dependencies between modules
 info:language:list                        Displays the list of available language locales
 info:timezone:list                        Displays the list of available timezones
maintenance
 maintenance:allow-ips                     Sets maintenance mode exempt IPs
 maintenance:disable                       Disables maintenance mode
 maintenance:enable                        Enables maintenance mode
 maintenance:status                        Displays maintenance mode status
module
 module:disable                            Disables specified modules
 module:enable                             Enables specified modules
 module:status                             Displays status of modules
 module:uninstall                          Uninstalls modules installed by composer
setup
 setup:backup                              Takes backup of Magento Application code base, media and database
 setup:config:set                          Creates or modifies the deployment configuration
 setup:cron:run                            Runs cron job scheduled for setup application
 setup:db-data:upgrade                     Installs and upgrades data in the DB
 setup:db-schema:upgrade                   Installs and upgrades the DB schema
 setup:db:status                           Checks if DB schema or data requires upgrade
 setup:di:compile                          Generates DI configuration and all missing classes that can be auto-generated
 setup:install                             Installs the Magento application
 setup:performance:generate-fixtures       Generates fixtures
 setup:rollback                            Rolls back Magento Application codebase, media and database
 setup:store-config:set                    Installs the store configuration
 setup:uninstall                           Uninstalls the Magento application
 setup:upgrade                             Upgrades the Magento application, DB data, and schema
We're sorry, an error occurred. Try clearing the cache and code generation directories. By default, they are: var/cache, var/di, var/generation, and var/page_cache.

Answer 1

This doesn't officially answer my question, but I got the code to work by adjusting my approach.

I changed the flow so that my main logic is in a Model and it's now being called from a Command which is fired from the CLI. This allows me to also call the Model from a Controller so that the website can leverage the same logic as the console.

Both run to completion with no errors now.