サーバーの導入時にyum listがレッスンしてくれました

今日は新しいサーバーを配備し、前のプロジェクトcopyを1部送って、走りたいと思っています.composerをインストールした後にinstallタイムズを使用するのは間違っています

[root@ecs-1ada-0317666 yedan_school]# 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
    - phpunit/phpunit 5.7.9 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.8 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.7 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.6 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.5 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.4 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.3 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.27 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.26 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.25 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.24 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.23 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.22 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.21 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.20 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.2 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.19 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.18 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.17 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.16 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.15 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.14 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.13 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.12 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.11 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.10 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.1 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - phpunit/phpunit 5.7.0 requires ext-dom * -> the requested PHP extension dom is missing from your system.
    - Installation request for phpunit/phpunit ~5.7 -> satisfiable by phpunit/phpunit[5.7.0, 5.7.1, 5.7.10, 5.7.11, 5.7.12, 5.7.13, 5.7.14, 5.7.15, 5.7.16, 5.7.17, 5.7.18, 5.7.19, 5.7.2, 5.7.20, 5.7.21, 5.7.22, 5.7.23, 5.7.24, 5.7.25, 5.7.26, 5.7.27, 5.7.3, 5.7.4, 5.7.5, 5.7.6, 5.7.7, 5.7.8, 5.7.9].

  To enable extensions, verify that they are enabled in your .ini files:
    - /etc/php.ini
    - /etc/php.d/bcmath.ini
    - /etc/php.d/bz2.ini
    - /etc/php.d/calendar.ini
    - /etc/php.d/ctype.ini
    - /etc/php.d/curl.ini
    - /etc/php.d/exif.ini
    - /etc/php.d/fileinfo.ini
    - /etc/php.d/ftp.ini
    - /etc/php.d/gd.ini
    - /etc/php.d/gettext.ini
    - /etc/php.d/gmp.ini
    - /etc/php.d/iconv.ini
    - /etc/php.d/json.ini
    - /etc/php.d/mbstring.ini
    - /etc/php.d/mysqli.ini
    - /etc/php.d/pdo.ini
    - /etc/php.d/pdo_mysql.ini
    - /etc/php.d/pdo_sqlite.ini
    - /etc/php.d/phar.ini
    - /etc/php.d/shmop.ini
    - /etc/php.d/simplexml.ini
    - /etc/php.d/sockets.ini
    - /etc/php.d/sqlite3.ini
    - /etc/php.d/tokenizer.ini
    - /etc/php.d/xml.ini
    - /etc/php.d/zip.ini
  You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.

ネット上で問題点を探したところ、composerパッケージに拡張依存とphp拡張があることがわかり、このPHP拡張(yum install php 71 w-xml)はインストールされていませんでした.(phpバージョン7.1)
しかし残念なことにyumについてはよく知っていると思い、yum list|grep xmlを使ってphp 71 w-xmlがあることに気づき、私の地元にはすでにこの拡張があると思っていたので、ずっとこの答えを気にせず、他の原因を探していました.後でyum listがインストール可能なすべてのパッケージをリストすることを意味していることがわかりました.ローカルにインストールされているパッケージを本当にリストしたのは、コマンドyum list installedです.だから次は同じミスを犯さないようにしっかり覚えておきましょう!!
添付https://www.cnblogs.com/AganRun/p/8118339.html):
1.YUMを使用してパッケージを検索コマンド:yum search 2.インストール可能なすべてのパッケージコマンドをリストします:yum list 3.更新可能なすべてのパッケージコマンドをリストします:yum list updates 4.インストールされているすべてのパッケージコマンドのリスト:yum list installed