Readme example error

[Matt-PMCT]

If I use the readme example:

use \ParagonIE\AntiCSRF\AntiCSRF;
$twigEnv->addFunction(
    new \Twig_SimpleFunction(
        'form_token',
        function($lock_to = null) {
            static $csrf;
            if ($csrf === null) {
                $csrf = new AntiCSRF;
            }
            return $csrf->insertToken($lock_to, false);
        },
        ['is_safe' => ['html']]
    )
);

if put just this in my twig file

{{ form_csrf() }}

I get an error stating that $lock_to must be a string, not null. Not sure if this is intended or not, but if I define lock_to as '' it works since it is a string now.

-Matt

[Nenglish7]

What type of error is it, Type out the exact output. Make the parameter that you are passing in the form_token function is a string. I noticed you tried {{ form_csrf() }}, but in the documentation it says to use {{ form_token() }}. The string parameter needs to be a local path.