$ sudo apt-get remove php5-json 

Uninstall php5-json including dependent package

If you would like to remove php5-json and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove php5-json 

Use Purging php5-json

If you use with purge options to php5-json package all the configuration and dependent packages will be removed.

$ sudo apt-get purge php5-json 

If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.

$ sudo apt-get purge --auto-remove php5-json 

See Also,