src/Authenticator.php
public function authenticate($identity, $credential)
    {
        $adapter = $this->auth->getAdapter();
        $adapter->setIdentity($identity);
        $adapter->setCredential($credential);

        return $this->auth->authenticate();
    }
public function authenticate($identity, $credential)
    {
        $adapter = $this->auth->getAdapter();
        $adapter->setIdentity($identity);
        $adapter->setCredential($credential);

        return $this->auth->authenticate();
    }
Authenticates user.

@param string $identity   User identifier (username, email, etc)
@param string $credential User password

@return Zend\Authentication\Result

@throws Zend\Authentication\Exception\RuntimeException