Magento 2 Fatal Error when running composer:install

Question

1. Clone fresh Magento 2 instance; 2.Run composer:install

Fatal Error: PHP Fatal error: Uncaught Error: Undefined class constant 'PRE_COMMAND_RUN'

Answer 1

This was an issue with Composer, By installing latest version of Composer solved it. The bug for the constant variable PRE_COMMAND_RUN is raised and closed.

Answer 2

You need install latest version of composer, upgrade steps given below.

-- Remove existing composer

Debian/Ubuntu

sudo apt-get remove composer

Centos/Redhat

sudo yum remove composer

Get the latest composer using wget.

cd /tmp
sudo curl -sS https://getcomposer.org/installer | php

Move composer executable to PATH so it can be accessible globally.

sudo mv composer.phar /usr/local/bin/composer

To check the composer version

composer -V