I successfully compiled the EmptyExtension and got salamander_php.so(my extension name).
Then I copied it to the php extension_dir and added the row to the php.ini
extension=salamander_php.so
when I input php -v I got the warning
PHP Warning: PHP Startup: Unable to load dynamic library '/usr/local/php7.1/lib/php/extensions/no-debug-zts-20160303/salamander_php.so' - /lib/libphpcpp.so.2.0:
undefined symbol: executor_globals in Unknown on line 0