Symfony 3 composer, ext-dom and ext-xml missing [duplicate]

Question

I am running Linux Mint 18.1. My IDE is PhpStorm and I am trying to install PHPUnit trough the composer. I followed the installation steps at https://getcomposer.org/download/.

Problem 1 - Installation request for phpunit/phpunit 6.4.x-dev -> satisfiable by phpunit/phpunit[6.4.x-dev]. - phpunit/phpunit 6.4.x-dev requires ext-dom * -> the requested PHP extension dom is missing from your system.
Problem 2 - symfony/symfony v3.3.6 requires ext-xml * -> the requested PHP extension xml is missing from your system. - symfony/symfony v3.3.6 requires ext-xml * -> the requested PHP extension xml is missing from your system. - symfony/symfony v3.3.6 requires ext-xml * -> the requested PHP extension xml is missing from your system. - Installation request for symfony/symfony (locked at v3.3.6, required as 3.3.*) -> satisfiable by symfony/symfony[v3.3.6].

Solutions I have tried:

• Install php-xml
• Install php7.0-xml
• This answer says to check if "extension=dom.so" is enabled in any of your php.ini files. It is not even present in my files

Any suggestions? Thanks a lot!

Answer 1

All you need to install from your terminal in Debian is:

sudo apt-get install php-xml

Or, if you're using PHP 7:

 sudo apt-get install php7.0-xml