Why I can't install php5 modules on Ubuntu 16.04?

Hello,

I have just finished setting up my Ubuntu 16.4 server. I have installed php5.6.26 because I am going to use Wordpress and I am not sure if all plugins are compatible with php7.

I need to install some php modules like php-xmlrpc or another module. When I type

sudo apt-get install php-curl php-gd php-mbstring php-mcrypt php-xml php-xmlrpc

This command is from this article on DO [How To Install WordPress with LAMP on Ubuntu 16.04] https://www.digitalocean.com/community/tutorials/how-to-install-wordpress-with-lamp-on-ubuntu-16-04 I get this message

 sudo apt-get install php-curl php-gd php-mbstring php-mcrypt php-xml php-xmlrpc
Reading package lists... Done
Building dependency tree
Reading state information... Done
php-gd is already the newest version (1:7.0+44+deb.sury.org~xenial+1).
The following additional packages will be installed:
  libcurl3 libxmlrpc-epi0 php7.0-curl php7.0-mbstring php7.0-mcrypt php7.0-xml php7.0-xmlrpc
The following NEW packages will be installed:
  libcurl3 libxmlrpc-epi0 php-curl php-mbstring php-mcrypt php-xml php-xmlrpc php7.0-curl php7.0-mbstring
  php7.0-mcrypt php7.0-xml php7.0-xmlrpc
0 upgraded, 12 newly installed, 0 to remove and 11 not upgraded.
Need to get 869 kB of archives.
After this operation, 2,943 kB of additional disk space will be used.
Do you want to continue? [Y/n]

Honestly I don’t want to use php7 and I have already explained why. How can I install the modules of php5, not php7?

What is the difference between modules for php7 and for php5? Can I still use php5 while the modules are for php7?

Thank you very much :)