array of required twig variables in symfony - php

Question

If there any way to discover the variables required from a Twig template? Example, if I had:
Hello {{ user }}! You're {{ age }} years old, well done big man!
I'd be able to load this template and then gather each of the required variables, eventually allowing me to have something like:
Array ( [0] => user [1] => age )
The end goal of this is to be able to define a view and then have the system create a form based on the required variables in a template file.

Answer 1

Working Solution
Thanks to morg for pointing me towards tokenize I was able to get what I wanted using the following (I placed it in my controller for testing):
$lexer = new \Twig_Lexer(new \Twig_Environment());
$stream = $lexer->tokenize(new \Twig_Source('{{test|raw}}{{test2|raw|asd}}{{another}}{{help_me}}', null));
$variables = array();
while (!$stream->isEOF()) {
$token = $stream->next();
if($token->getType() === \Twig_Token::NAME_TYPE){
$variables[] = $token->getValue();
while (!$stream->isEOF() && $token->getType() !== \Twig_Token::VAR_END_TYPE) {
$token = $stream->next();
}
}
}
$variables = array_unique($variables);
This returns:
Array
(
[0] => test
[1] => test2
[2] => another
[3] => help_me
)
You'll notice I only get variables and not any of the functions (this is through design), although you could remove the nested while loop if you wish to get both variables and functions.

Answer 2

You can use the twig tokenizer for this.
$stream = $twig->tokenize($source, $identifier);
The tokenizer has a toString() Method, whose resulting string you can parse for
VAR_START_TYPE()
NAME_TYPE(varname)
VAR_END_TYPE()
Look at this for more detailed information.

Answer 3

You can try using preg_match_all('{{\s*(\w+)\s*}}', 'template {{string }} with {{ var}}', $matchesArray);. The $matchArray is structured as following:
Array(
0 => array(0 => '{{string }}', 1 => 'string'),
1 => array(0 => '{{ var}}', 1 => 'var')
)

Answer 4

Another way of doing this from inside PHP code is not elegant, but still more reliable than any regex will be:
$source = "My template string with {{ some }} parameters.";
$stream = $twig->tokenize(new \Twig_Source($source, "source"));
$matches = [];
preg_match_all(
"/NAME_TYPE\((.*)\)/", $stream->__toString(), $matches
);
if (count($matches) > 1) {
$params = array_unique($matches[1]);
} else {
$params = [];
}
This works by using Twig internal mechanisms to tokenize the template string and then extract parameters names with a regex.
Edit: The previous version of my answer used the parse method to create a tree of nodes, but it didn’t seem to work anymore, and matching on NAME_TYPE at the previous step seems more reliable, not sure if I missed something there…