Installation fail

[stepzerosolutions]

How to reproduce
Install the extension using pecl install ds
Add extension to php.ini file using extension=ds.so
sudo apache2ctl graceful
Installation success and I can see the extension so file in extension directory.

However when I run phpinfo() I can't see any extension details in the extensions section
When I try to run simple example http://php.net/manual/en/ds.examples.php it gives me error 500
details in error.log is

PHP Fatal error: Uncaught Error: Class 'Ds\Vector' not found in /var/www/html/test.php:2\nStack trace:\n#0 {main}\n thrown in /var/www/html/test.php on line 2

System details
Apache 2
Ubuntu 16:04

[rtheunissen]

Did you add it to the correct .ini? What does php -m say?

[stepzerosolutions]

It doesn't load ds. I've add it to correct php.ini /etc/php/7.0/apache2/php.ini
I'll come back to you later tomorrow.

Documentation says "Note: please load this extension after json extension,otherwise can't load this extension." do you know how to add it after json?

[stepzerosolutions]

I get following error when I use php -v

PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/20151012/ds.so' - /usr/lib/php/20151012/ds.so: undefined symbol: php_json_serializable_ce in Unknown on line 0

[rtheunissen]

See #2