How to install a PHP client to work with the retailCRM API on Open SERVER?

Question

API

Open Server 5.2.4
I can't install https://github.com/retailcrm/api-client-php
I put the files in the folder with the site, in the console I execute

Microsoft Windows [Version 6.3.9600]

[email protected] c:\openserver
$ cd C:\openserver\domains\my.loc

[email protected] C:\OpenServer\domains\my.loc
$ composer install
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for phpunit/php-code-coverage 3.3.0 -> satisfiable by phpunit/php-code-coverage[3.3.0].
    - phpunit/php-code-coverage 3.3.0 requires php ^5.6 || ^7.0 -> your PHP version (5.3.29) does not satisfy that requirement.
  Problem 2
    - Installation request for phpunit/php-invoker 1.1.4 -> satisfiable by phpunit/php-invoker[1.1.4].
    - phpunit/php-invoker 1.1.4 requires ext-pcntl * -> the requested PHP extension pcntl is missing from your system.
  Problem 3
    - phpunit/phpunit 5.2.9 requires php ^5.6 || ^7.0 -> your PHP version (5.3.29) does not satisfy that requirement.
    - phpunit/phpunit 5.2.8 requires php ^5.6 || ^7.0 -> your PHP version (5.3.29) does not satisfy that requirement.
    - phpunit/phpunit 5.2.7 requires php >=5.6 -> your PHP version (5.3.29) does not satisfy that requirement.
    - phpunit/phpunit 5.2.6 requires php >=5.6 -> your PHP version (5.3.29) does not satisfy that requirement.
    - phpunit/phpunit 5.2.5 requires php >=5.6 -> your PHP version (5.3.29) does not satisfy that requirement.
    - phpunit/phpunit 5.2.4 requires php >=5.6 -> your PHP version (5.3.29) does not satisfy that requirement.
    - phpunit/phpunit 5.2.3 requires php >=5.6 -> your PHP version (5.3.29) does not satisfy that requirement.
    - phpunit/phpunit 5.2.2 requires php >=5.6 -> your PHP version (5.3.29) does not satisfy that requirement.
    - phpunit/phpunit 5.2.12 requires php ^5.6 || ^7.0 -> your PHP version (5.3.29) does not satisfy that requirement.
    - phpunit/phpunit 5.2.11 requires php ^5.6 || ^7.0 -> your PHP version (5.3.29) does not satisfy that requirement.
    - phpunit/phpunit 5.2.10 requires php ^5.6 || ^7.0 -> your PHP version (5.3.29) does not satisfy that requirement.
    - phpunit/phpunit 5.2.1 requires php >=5.6 -> your PHP version (5.3.29) does not satisfy that requirement.
    - phpunit/phpunit 5.2.0 requires php >=5.6 -> your PHP version (5.3.29) does not satisfy that requirement.
    - Installation request for phpunit/phpunit 5.2.* -> satisfiable by phpunit/phpunit[5.2.0, 5.2.1, 5.2.10, 5.2.11, 5.2.12, 5.2.2, 5.2.3, 5.2.4, 5.2.5, 5.2.6, 5.2.7, 5.2.8,
 5.2.9].

  To enable extensions, verify that they are enabled in those .ini files:
    - C:\OpenServer\modules\php\PHP-5.3\php.ini
  You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.

I'm not very good at this as far as I'm concerned. What could be the problem??
Already tired of looking for a solution ((( Help please!

Answer 1

Your PHP is old. What you bet requires a minimum of 5.6.