古いバージョンのLaravelにlaravel-ide-helperをインストールする

Laravel 5.8 を使った既存の環境に laravel-ide-helper をインストールしようとしたら上手く行かなかった。
（Laravelの最新バージョンは8）


```
[y_ito@nnn.nnn.nnn.nnn laravel_study]$ composer require --dev barryvdh/laravel-ide-helper
Using version ^2.9 for barryvdh/laravel-ide-helper
./composer.json has been updated
Running composer update barryvdh/laravel-ide-helper
Loading composer repositories with package information
Updating dependencies
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - barryvdh/laravel-ide-helper[dev-master, v2.9.0] require illuminate/console ^8 -> found illuminate/console[v8.0.0, ..., 8.x-dev] but these were not loaded, likely because it conflicts with another require.
    - barryvdh/laravel-ide-helper 2.9.x-dev is an alias of barryvdh/laravel-ide-helper dev-master and thus requires it to be installed too.
    - Root composer.json requires barryvdh/laravel-ide-helper ^2.9 -> satisfiable by barryvdh/laravel-ide-helper[v2.9.0, 2.9.x-dev (alias of dev-master)].


Installation failed, reverting ./composer.json and ./composer.lock to their original content.
```

laravel-ide-helper v2.9.0（最新版？） には illuminate/console バージョン8以上が必要ということらしい。
なのでインストールする laravel-ide-helper のバージョンを下げることにする。
Laravel 5.8 と 6 の間にリリースされた laravel-ide-helper である v.2.6.3（2019-08-31リリース）をインストールしてみた。
`composer require` でバージョンを指定したらインストールできた。

```
[y_ito@nnn.nnn.nnn.nnn laravel_study]$ composer require --dev barryvdh/laravel-ide-helper:"2.6.3"
./composer.json has been updated
Running composer update barryvdh/laravel-ide-helper
Loading composer repositories with package information
Updating dependencies
Lock file operations: 11 installs, 0 updates, 0 removals
  - Locking barryvdh/laravel-ide-helper (v2.6.3)
  - Locking barryvdh/reflection-docblock (v2.0.6)
  - Locking composer/ca-bundle (1.2.9)
  - Locking composer/composer (1.10.20)
  - Locking composer/semver (1.7.2)
  - Locking composer/spdx-licenses (1.5.5)
  - Locking composer/xdebug-handler (1.4.5)
  - Locking justinrainbow/json-schema (5.2.10)
  - Locking seld/jsonlint (1.8.3)
  - Locking seld/phar-utils (1.1.1)
  - Locking symfony/filesystem (v5.2.4)
Writing lock file
Installing dependencies from lock file (including require-dev)
Package operations: 11 installs, 0 updates, 0 removals
  - Downloading symfony/filesystem (v5.2.4)
  - Downloading seld/phar-utils (1.1.1)
  - Downloading seld/jsonlint (1.8.3)
  - Downloading justinrainbow/json-schema (5.2.10)
  - Downloading composer/xdebug-handler (1.4.5)
  - Downloading composer/spdx-licenses (1.5.5)
  - Downloading composer/semver (1.7.2)
  - Downloading composer/ca-bundle (1.2.9)
  - Downloading composer/composer (1.10.20)
  - Downloading barryvdh/reflection-docblock (v2.0.6)
  - Downloading barryvdh/laravel-ide-helper (v2.6.3)
  - Installing symfony/filesystem (v5.2.4): Extracting archive
  - Installing seld/phar-utils (1.1.1): Extracting archive
  - Installing seld/jsonlint (1.8.3): Extracting archive
  - Installing justinrainbow/json-schema (5.2.10): Extracting archive
  - Installing composer/xdebug-handler (1.4.5): Extracting archive
  - Installing composer/spdx-licenses (1.5.5): Extracting archive
  - Installing composer/semver (1.7.2): Extracting archive
  - Installing composer/ca-bundle (1.2.9): Extracting archive
  - Installing composer/composer (1.10.20): Extracting archive
  - Installing barryvdh/reflection-docblock (v2.0.6): Extracting archive
  - Installing barryvdh/laravel-ide-helper (v2.6.3): Extracting archive
2 package suggestions were added by new dependencies, use `composer suggest` to see details.
Package fzaninotto/faker is abandoned, you should avoid using it. No replacement was suggested.
Package phpunit/php-token-stream is abandoned, you should avoid using it. No replacement was suggested.
Generating optimized autoload files
> Illuminate\Foundation\ComposerScripts::postAutoloadDump
> @php artisan package:discover --ansi
Discovered Package: barryvdh/laravel-ide-helper
Discovered Package: beyondcode/laravel-dump-server
Discovered Package: fideloper/proxy
Discovered Package: laravel/tinker
Discovered Package: nesbot/carbon
Discovered Package: nunomaduro/collision
Package manifest generated successfully.
61 packages you are using are looking for funding.
Use the `composer fund` command to find out more!
```

最後のメッセージが気になる。
これは「開発に対して資金援助をお願いします」っていうことかな？

##参考ページ
[Laravel開発で役立つlaravel-ide-helper | 株式会社スタイラジーの「居心地の良い」ブログ](https://ameblo.jp/stylagy/entry-12584727173.html)
[laravel5.8にlaravel-ide-helperを入れてみた - Qiita](https://qiita.com/yoshinyan/items/4b2fc481b218f776ba0f)
[よく使うcomposerコマンドとバージョン指定方法の備忘録 | tanden techblog](https://tanden.dev/%E3%82%88%E3%81%8F%E4%BD%BF%E3%81%86composer%E3%82%B3%E3%83%9E%E3%83%B3%E3%83%89%E3%81%A8%E3%83%90%E3%83%BC%E3%82%B8%E3%83%A7%E3%83%B3%E6%8C%87%E5%AE%9A%E3%81%AE%E5%82%99%E5%BF%98%E9%8C%B2/)