by Ken Task.
sudo service php5-fpm restart
'spirit of sharing', Ken
Don't run Ubuntu, but ...
http://iteration9.com/2013/php-json-licensing-and-php-5-5/
is worth a read - which also offers alternative methods for getting support (shows yum but assume one could use a ubuntu repo for same)
And ...
http://askubuntu.com/questions/361424/what-happened-to-json-encode-in-13-10-php
which says to
sudo service php5-fpm restart
'spirit of sharing', Ken