Ne pas utiliser apt, la version qu’il installe va générer des erreurs.

PHP Fatal error: Uncaught Error: Call to undefined method Composer\Package\RootPackage::getConfig() in /home/manu/.config/composer/vendor/fxp/composer-asset-plugin/Config/ConfigBuilder.php:111
Stack trace:
#0 /home/manu/.config/composer/vendor/fxp/composer-asset-plugin/Config/ConfigBuilder.php(74): Fxp\Composer\AssetPlugin\Config\ConfigBuilder::getConfigBase(Object(Composer\Composer), Object(Composer\IO\ConsoleIO))
#1 /home/manu/.config/composer/vendor/fxp/composer-asset-plugin/FxpAssetPlugin.php(82): Fxp\Composer\AssetPlugin\Config\ConfigBuilder::build(Object(Composer\Composer), Object(Composer\IO\ConsoleIO))
#2 /usr/share/php/Composer/Plugin/PluginManager.php(215): Fxp\Composer\AssetPlugin\FxpAssetPlugin->activate(Object(Composer\Composer), Object(Composer\IO\ConsoleIO))
#3 /usr/share/php/Composer/Plugin/PluginManager.php(188): Composer\Plugin\PluginManager->addPlugin(Object(Fxp\Composer\AssetPlugin\FxpAssetPlugin))
#4 /usr/share/php/Composer/Plugin/PluginManager.php(240): Composer\Plugin\PluginManager->registerPackage(Obje in /home/manu/.config/composer/vendor/fxp/composer-asset-plugin/Config/ConfigBuilder.php on line 111

Si vous l’avez déjà installée, supprimez la avec

sudo apt-get remove composer

ensuite, tapez la commande suivante dans un terminal:

curl -sS https://getcomposer.org/installer | sudo php -- --install-dir=/usr/bin --filename=composer

Et ça fonctionne