How to install mbstring in Ubuntu 17.04?

问题

I have php version 7.0.22. I tried doing

sudo apt-get install mbstring ,
sudo apt-get install php-mbstring ,
sudo apt-get install php7.0-mbstring

but every time it says Unable to locate package mbstring

Please help.

来源：https://stackoverflow.com/questions/46733510/how-to-install-mbstring-in-ubuntu-17-04