Yii 2 not installing packages?

Question

Yii

Win 7
Installed Yii 2-2.0.15.1
PHP 5.6
OpenServer
trying to install Select2
php composer.phar require kartik-v/yii2-widget-select2 "*"
gives error

Your requirements could not be resolved to an installable set of packages.
Problem 1
- phpunit/phpunit 6.5.7 requires php ^7.0 -> your PHP version (5.6.12) does not satisfy that requirement.
- phpunit/phpunit 6.5.7 requires php ^7.0 -> your PHP version (5.6.12) does not satisfy that requirement.
- phpunit/phpunit 6.5.7 requires php ^7.0 -> your PHP version (5.6.12) does not satisfy that requirement.
- Installation request for phpunit/phpunit (locked at 6.5.7) -> satisfiable by phpunit/phpunit[6.5.7].
Installation failed, reverting ./composer.json to its original content.

composer.json

{
    "name": "yiisoft/yii2-app-basic",
    "description": "Yii 2 Basic Project Template",
    "keywords": ["yii2", "framework", "basic", "project template"],
    "homepage": "http://www.yiiframework.com/",
    "type": "project",
    "license": "BSD-3-Clause",
    "support": {
        "issues": "https://github.com/yiisoft/yii2/issues?state=open",
        "forum": "http://www.yiiframework.com/forum/",
        "wiki": "http://www.yiiframework.com/wiki/",
        "irc": "irc://irc.freenode.net/yii",
        "source": "https://github.com/yiisoft/yii2"
    },
    "minimum-stability": "stable",
    "require": {
        "php": ">=5.4.0",
        "yiisoft/yii2": "~2.0.14",
        "yiisoft/yii2-bootstrap": "~2.0.0",
        "yiisoft/yii2-swiftmailer": "~2.0.0",
        "kartik-v/yii2-widget-select2": "*"
    },
    "require-dev": {
        "yiisoft/yii2-debug": "~2.0.0",
        "yiisoft/yii2-gii": "~2.0.0",
        "yiisoft/yii2-faker": "~2.0.0",

        "codeception/base": "^2.2.3",
        "codeception/verify": "~0.3.1",
        "codeception/specify": "~0.4.3"
    },
    "config": {
        "process-timeout": 1800,
        "fxp-asset": {
            "enabled": false
        }
    },
    "scripts": {
        "post-install-cmd": [
            "yii\\composer\\Installer::postInstall"
        ],
        "post-create-project-cmd": [
            "yii\\composer\\Installer::postCreateProject",
            "yii\\composer\\Installer::postInstall"
        ]
    },
    "extra": {
        "yii\\composer\\Installer::postCreateProject": {
            "setPermission": [
                {
                    "runtime": "0777",
                    "web/assets": "0777",
                    "yii": "0755"
                }
            ]
        },
        "yii\\composer\\Installer::postInstall": {
            "generateCookieValidationKey": [
                "config/web.php"
            ]
        }
    },
    "repositories": [
        {
            "type": "composer",
            "url": "https://asset-packagist.org"
        }
    ]
}

Answer 1

1) Put the version below the plugins.
2) Run composer without requirements.

Answer 2

So read the error you indicated to the composer that you have 5 php and the module requires 7

Answer 3

Update php to 7.0 at least.

Answer 4

OK. I will upgrade to 7. ATP.