I couldn’t find instructions anywhere for installing composer in Manjaro. I managed to get it working using the technique described for Arch in this article but had to do the steps in a different order.

Editing php.ini

In Manjaro we need to change the php.ini file so that Composer can install.

Open php.ini for editing from the command line:

sudo gedit /etc/php/php.ini

Locate and uncomment the following lines:

extension=openssl.so
extension=phar.so

Search (ctrl + f) for the open_basedir and add the following to the end of the line:

:/usr/local/bin/:/root/

Save and close the php.ini file.

Downloading and Installing Composer

Download and install Composer from the command line:

curl -sS https://getcomposer.org/installer | php
sudo mv composer.phar /usr/local/bin/composer

Restart the httpd server:

sudo systemctl restart httpd

Update composer:

sudo composer self-update

That should be everything sorted!