get value of input in casperjs

Hi allm I would like to know how to get an input value with casperjs This is my html element ``` <input type="hidden" name="key" value="newkey"> ``` This is what I have tried: ``` view = 'users/registered'; casper.test.begin("Activating account", 5, function register(test){ casper.start(webroot + view, function(){ }).then(function(){ this.echo("Retrieving data from hidden input key", "COMMENT"); activationKey = this.evaluate(function() { return __utils__.getFieldValue('key'); }); }).then(function(){ this.echo("Activating account with the key \"" + activationKey + "\"", "COMMENT"); window.location = webroot + activationKey; }); casper.run(function() { this.echo('Account activated successfully', 'SUCCESS').exit(); test.done(); }); }); casper.viewport(page.width, page.height); ``` In this case return `null` I have also tried: ``` activationKey = __utils__.getFieldValue('key'); ``` but return me this error: ``` FAIL ReferenceError: Can't find variable: __utils__ ```