SHELL

Remove composer for ubuntu

sudo apt-get remove composer

ubuntu composer uninstall

//Uninstall composer
sudo apt-get remove composer

//Uninstall composer and it dependent packages
sudo apt-get autoremove composer

//Purging composer
sudo apt-get purge composer
sudo apt-get autoremove --purge composer

ubuntu uninstall composer

Delete the file composer.phar.
Delete the Cache Folder:
Linux: /home/<user>/.composer
Windows: C:Users<username>AppDataRoamingComposer