Returns true if the given userLogin is known in the database

@param string $userLogin
@return bool true if the user is known
164883
public function userExists($userLogin)
    {
        if ($userLogin == 'anonymous') {
            return true;
        }

        Piwik::checkUserIsNotAnonymous();
        Piwik::checkUserHasSomeViewAccess();

        if ($userLogin == Piwik::getCurrentUserLogin()) {
            return true;
        }

        return $this->model->userExists($userLogin);
    }
265611
public function isLogged(UserServiceInterface $userService)
    {
        $user = $this->getAndLogUserByCookie($userService);
        if ($user) {
            $this->refreshRememberCookie($user, false);
            return true;
        } else {
            return false;
        }
    }
136210
public function login($login, $password) {
		$user = $this->findUser($login);

		if ($user) {
			$this->user = $user;
			$this->recognized = true;

			if ($this->verifyUser($user, $password)) {
				$this->authenticated = true;

				$session = $this->findSession($user);
				if ($session === null) {
					$session = $this->createSession($user);
				}

				$this->session = $session;
				return true;
			}
		}

		return false;
	}
630088
public function isLoggedIn()
    {
        $response = $this->client->get($this->uri());

        try {
            $body = $this->handleResponse($response)->getDecodedData();
        } catch (ClientException $exception) {
            return false;
        }

        return property_exists(
            $body,
            'user'
        );
    }
255961
public function isLoggedIn()
    {
        if ($this->instance instanceof \Phavour\Session\Storage) {
            if ($this->instance->get('identity') != false) {
                return true;
            }
        }

        return false;
    }
53378
public function findByLogin($login)
	{
		$model = $this->createModel();

		if ( ! $user = $model->newQuery()->where($model->getLoginName(), '=', $login)->first())
		{
			throw new UserNotFoundException("A user could not be found with a login value of [$login].");
		}

		return $user;
	}
43335
public function findByLogin($login)
    {
        try
        {
            return $this->sentry->findUserByLogin($login);
        }
        catch (SentryUserNotFoundException $e)
        {
            throw new UserNotFoundException($e->getMessage());
        }
    }
1349172
public function is_login( $table_name ){
		$user_info = $this->get_login_user_info( $table_name );
		if( $user_info === false ){
			return false;
		}
		return true;
	}
354009
protected function checkUserPassword($username, $password)
    {
        if (!isset($this->users[$username]) || $this->users[$username] !== $password) {
            return false;
        }

        return true;
    }
1040583
public function isLoggedIn()
    {
        $loggedIn = $this->di->get("session")->has("user");
        if (!$loggedIn) {
            $this->di->get("response")->redirect("user/login");
            return false;
        }
        return true;
    }
1007806
public function isVisibleFor($login)
    {
        $personalVisibility = parent::isVisibleFor($login);
        if (!$personalVisibility) {
            return $personalVisibility;
        }


        foreach ($this->getChilds() as $childItem) {
            if ($childItem->isVisibleFor($login)) {
                return true;
            }
        }

        return false;
    }
413416
public static function isExistByUsername( $username ) {

		$user = self::find()->where( 'username=:username', [ ':username' => $username ] )->one();

		return isset( $user );
	}
1338689
public function login(string $username, string $password)
    {
        $this->userInfo = $this->makeRequest('POST', 'login', compact('username', 'password'));

        if (!isset($this->userInfo['error']) && isset($this->userInfo['data']['id'])) {
            return true;
        }

        return false;
    }
247089
public function hasPermission($login, $permission)
    {
        $groupName = $this->getLoginGroupName($login);

        // if login has no groups, no permission
        if ($groupName === null) {
            return false;
        }
        // master admin has all permissions
        if ($groupName == 'master_admin') {
            return true;
        }

        $permissions = $this->getGroupPermissions($groupName);

        return in_array($permission, $permissions);
    }
371013
public static function isUser(string $username): bool {
		$userdbname = setup::getValidation("username");
		if (R::findOne('user', ' ' . $userdbname . ' = ? ', [$username])) {
			return true;
		}

		return false;
	}
924143
public static function isLoggedIn()
    {
        // Check to see if Symphony exists, or if we already have an Author instance.
        if (is_null(self::$_instance) || self::$Author) {
            return true;
        }

        // No author instance found, attempt to log in with the cookied credentials
        return self::login(self::$Cookie->get('username'), self::$Cookie->get('pass'), true);
    }
267984
public static function loginUser( $login, $password, $authenticationMatch = false )
    {
        $user = self::_loginUser( $login, $password, $authenticationMatch );

        if ( is_object( $user ) )
        {
            self::loginSucceeded( $user );
            return $user;
        }
        else
        {
            self::loginFailed( $user, $login );
            return false;
        }
    }