I'd like to define form fields for input based on a template's variables.
Therefore I figured out that a templating engine needs something like a introspection so that I'm able to retrieve the template's variables.
Smarty just offers a list of assigned variables and as far as I know Twig just in Debug mode. Do you know how I could solve this besides writing my own engine?
Thanks in advance
Edit to clarify: If there is something like {{ foo }} I want to get a string with the variable name out of the template. Is this possible?
In twig you have the special variable _context. This is a variable which holds all known variables inside a template. You can check which variables it hold by looping the variable e.g.
{% for key in _context|keys %}
{{ key }}<br />
{% endfor %}
You also can use this variable to access dynamic variables e.g.
{% set my_fixed_var_bar = 'foobar' %}
{% set foo = 'bar' %}
{{ _context['my_fixed_var_'~bar]| default('N/A') }} {# with array notation #}
{{ attribute(_context, 'my_fixed_var_'~foo) | default('N/A') }} {# with attribute function #}
Macros are an exception as they have their own (variable) scope in twig. This means they do not share the global _context variable and rather have their own. If you want to access variables from outside the macro, you'd just have to pass the _context to the macro e.g.
{% import _self as 'macros' %}
{% macro foo(context) %}
{{ _context | keys | length }} {# 0 #}
{{ context.my_fixed_var_bar }} {# foobar #}
{% endmacro %}
{{ macros.foo() }} {# 0 foobar #}
If you need to access the variable _context inside a function/filter/extension class you can achieve this by setting the option needs_context to true
$twig->addFunction(new \Twig\TwigFunction('my_function', function($context) {
//do stuff
}, [ 'needs_context' => true, ]));