erreur installation Laravel v 5.4 avec le compositeur dans ubuntu

Question

hey une erreur get lorsque l'installation Laravel v-5,4

une erreur de ça:

Le fichier "http://packagist.org/p/provider-2016%24e217873bdc8408956b33b1eb317ad1182d3a82fde9a746cc5e7def6135696f96.json" ne pouvait pas être téléchargé (HTTP /1.1 Erreur interne du serveur 500) http://packagist.org n'a pas pu être entièrement chargé, les informations de package ont été chargées à partir du cache local et peuvent être périmées Installation de laravel/laravel (v5.5.0) - Installation de laravel/laravel (v5.5.0) : Téléchargement depuis le cache Projet créé dans le blog @php -r "file_exists ('. Env') || copie ('env.example', '.env'); » dépôts de compositeur de chargement avec des informations de package dépendances de mise à jour (y compris require-dev)

Impossible de décoder la réponse: zlib_decode(): erreur de données Retrying avec mode dégradé, vérifiez https://getcomposer.org/doc/articles/troubleshooting. md #-mode dégradé pour plus d'informations Vos exigences ne peuvent pas être résolus à un ensemble installable de paquets.

Problem 1 
- phpunit/phpunit 6.4.1 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.4.0 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.3.1 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.3.0 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.2.4 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.2.3 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.2.2 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.2.1 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.2.0 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.1.4 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.1.3 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.1.2 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.1.1 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.1.0 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.9 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.8 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.7 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.6 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.5 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.4 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.3 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.2 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.13 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.12 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.11 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.10 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.1 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- phpunit/phpunit 6.0.0 requires ext-dom * -> the requested PHP extension dom is missing from your system. 
- Installation request for phpunit/phpunit ~6.0 -> satisfiable by phpunit/phpunit[6.0.0, 6.0.1, 6.0.10, 6.0.11, 6.0.12, 6.0.13, 6.0.2, 6.0.3, 6.0.4, 6.0.5, 6.0.6, 6.0.7, 6.0.8, 6.0.9, 6.1.0, 6.1.1, 6.1.2, 6.1.3, 6.1.4, 6.2.0, 6.2.1, 6.2.2, 6.2.3, 6.2.4, 6.3.0, 6.3.1, 6.4.0, 6.4.1]. 

s'il vous plaît me aider pour finir ce problème. J'ai essayé mais mais aucun résultat

Answer 1

Si vous utilisez PHP 7 ou version ultérieure, vous pouvez installer ext-dom en exécutant la commande suivante:

sudo apt-get install php7.0-xml // for PHP 7 
sudo apt-get install php7.1-xml // for PHP 7