How to retrieve all Variables from a Twig Template?

Is it possible to retrieve all variables inside a Twig template with PHP?

Example someTemplate.twig.php:

Hello {{ name }}, 
your new email is {{ email }}

Now I want to do something like this:

$template = $twig->loadTemplate('someTemplate');
$variables = $template->getVariables();

$variables should now contain “name” and “email”.

The reason I want to do this is that I am working on a CMS system where my twig templates and variables are dynamically set by my users and they also fill the variables through an API.

I want to set default values to not-set variables and therefore I need a list of all variables that exist inside the template…

Answer

UPDATE 2019

Although {{ dump() }} does work, in some circumstances it may result in a “memory exhausted” error from PHP if it generates too much information (for example, due to recursion). In this case, try {{ dump(_context|keys) }} to get a list of the defined variables by name without dumping their contents.

UPDATE 2017

It is possible by using {{ dump() }} filter. Thanks for pointing that out in the comments!

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OUTDATED

It is not possible.

You can look for these variable in twig templates and add |default('your_value') filter to them. It will check if variable is defined and is not empty, and if no – will replace it with your value.