I wish this helpful for you My solution was to dump mamp and use Zend Server CE. This worked perfectly fine for me. A minor tweak to my php.ini file to turn html_errors on and that was it. All extensions apart from xdebug were installed already. I was even able to copy the intl.so extension to my mamp directory and it worked there to but I preferred having zend using less resources. Rather than a gui it uses my browser window which I can close if I don't need it open. i actually saw a post on here recommending zend server ce and that was what prompted me to download it. No problems ever since.
Do PHP 5.5' intl extension and PECL intl package origin from the same source code?
this one helps. When using twig with Symfony, you should register the extension as a service in your services.yaml file. If installed using the twig/extensions flex recipe, it will provide the config/packages/twig_extensions.yaml file, you just have to uncomment the desired extensions (see the original comment on github).
# Uncomment any lines below to activate that Twig extension