Twig "Unable to add function" - php

Question

I'm using twig, and i'm attempting to add a function.
$Func = new \Twig_SimpleFunction('placeholder', function ($title) {
$this->module->CurrentPage->addPlaceholder($title);
});
\App::make('twig')->addFunction($Func);
I will get the following exception
Unable to add function "placeholder" as extensions have already been initialized.
I've checked twice that the "addFunction" is executed before the twig "loadTemplate". So, it does not seem to be the problem.
Does anyone have a hint, or an idea about this? Or what its all about.
Thanks in advance.

Answer 1

You need to add twig functions right after you created Twig_Environment instance. For example, the following WILL NOT work:
$loader = new Twig_Loader_Filesystem($this->resourceRoot . '/views');
$twig = new Twig_Environment($loader, array(
'cache' => storage_path('twig'),
'debug' => Config::get('app.debug'),
'strict_variables' => true,
));
$lexer = new Twig_Lexer($twig, array(
'tag_comment' => array('{#', '#}'),
'tag_block' => array('{%', '%}'),
'tag_variable' => array('{^', '^}'),
'interpolation' => array('#{', '}'),
));
$twig->setLexer($lexer);
$function = new Twig_SimpleFunction('widget', function ($widget, array $params) {
WidgetFactory::renderWidget($widget, $params);
});
$twig->addFunction($function);
Because Lexer is initialized before functions are added. You need to make it like this:
$loader = new Twig_Loader_Filesystem($this->resourceRoot . '/views');
$twig = new Twig_Environment($loader, array(
'cache' => storage_path('twig'),
'debug' => Config::get('app.debug'),
'strict_variables' => true,
));
$function = new Twig_SimpleFunction('widget', function ($widget, array $params) {
WidgetFactory::renderWidget($widget, $params);
});
$twig->addFunction($function);
$lexer = new Twig_Lexer($twig, array(
'tag_comment' => array('{#', '#}'),
'tag_block' => array('{%', '%}'),
'tag_variable' => array('{^', '^}'),
'interpolation' => array('#{', '}'),
));
$twig->setLexer($lexer);