Creating ReflectionFunction in Zend Framework 2 failed

I am trying to create object from type ReflectionFunction using the static function reflectFunction in Zend\Server\Reflection class. When I call this function from my controller it gives me this error:

Invalid function "userSignIn" passed to reflectFunction

That means that function userSignIn does not exist but this function exist in my TextServer php file.

Here is the code from TextServer class:

public function __construct(){
    echo "TextServer: constructor";
    parent::__construct();
    $this->addUserSignInFunction();
    $this->addUserInsertTextFunction();
}

/**
 * Creating ReflectionFunction for userSignIn function
 */
public function addUserSignInFunction(){
    $function = Reflection::reflectFunction('userSignIn');
    $this->addFunction($function);
}

/**
 * Creating ReflectionFunction for userInsertText function
 */
public function addUserInsertTextFunction(){
    $function = Reflection::reflectFunction('userInsertText');
    $this->addFunction($function);
}

Here is the code in the controller:

    public function  indexAction(){

    $s = new TextServer();

    return new ViewModel(array('texts' =>  $this->getTextTable()->fetchAll(),
            'users' => $this -> getUserTable()->fetchAll(),
            'user_id' => $_SESSION["user_id"]));
     }