Class 'SimpleXmlElement' not found - after installing Evo 3.1.8

[q2apro]

1. I installed Evo CMS.
2. I clicked on "Save" at the Settings, leaving them unchanged.
3. I got this error message:

Undefined index: SERVER_PORT
« Evolution CMS Parse Error »
Class 'SimpleXmlElement' not found (View: /var/www/html/manager/views/page/2.blade.php)
Error information   
File    /var/www/html/core/functions/rss.php
Line    14
EQUEST_URI  http://xxxx/manager/index.php?a=2
Manager action  2 - Viewing dashboard

Backtrace:

Backtrace
--
Illuminate\Support\Facades\Facade::__callStatic()manager/index.php on line 162
EvolutionCMS\ManagerTheme->handleRoute()core/vendor/illuminate/support/Facades/Facade.php on line 261
Illuminate\Routing\Router->dispatch()core/src/ManagerTheme.php on line 408
Illuminate\Routing\Router->dispatchToRoute()core/vendor/illuminate/routing/Router.php on line 625
Illuminate\Routing\Router->runRoute()core/vendor/illuminate/routing/Router.php on line 636
Illuminate\Routing\Router->runRouteWithinStack()core/vendor/illuminate/routing/Router.php on line 672
Illuminate\Pipeline\Pipeline->then()core/vendor/illuminate/routing/Router.php on line 697
Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}()core/vendor/illuminate/pipeline/Pipeline.php on line 103
EvolutionCMS\Middleware\VerifyCsrfToken->handle()core/vendor/illuminate/pipeline/Pipeline.php on line 167
Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}()core/src/Middleware/VerifyCsrfToken.php on line 13
EvolutionCMS\Middleware\Manager->handle()core/vendor/illuminate/pipeline/Pipeline.php on line 167
Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}()core/src/Middleware/Manager.php on line 25
Illuminate\Session\Middleware\StartSession->handle()core/vendor/illuminate/pipeline/Pipeline.php on line 167
Illuminate\Session\Middleware\StartSession->handleStatefulRequest()core/vendor/illuminate/session/Middleware/StartSession.php on line 64
Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}()core/vendor/illuminate/session/Middleware/StartSession.php on line 121
Illuminate\Routing\Middleware\SubstituteBindings->handle()core/vendor/illuminate/pipeline/Pipeline.php on line 167
Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}()core/vendor/illuminate/routing/Middleware/SubstituteBindings.php on line 50
Illuminate\View\Middleware\ShareErrorsFromSession->handle()core/vendor/illuminate/pipeline/Pipeline.php on line 167
Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}()core/vendor/illuminate/view/Middleware/ShareErrorsFromSession.php on line 49
Illuminate\Routing\Router->Illuminate\Routing\{closure}()core/vendor/illuminate/pipeline/Pipeline.php on line 128
Illuminate\Routing\Route->run()core/vendor/illuminate/routing/Router.php on line 695
Illuminate\Routing\Route->runController()core/vendor/illuminate/routing/Route.php on line 205
Illuminate\Routing\ControllerDispatcher->dispatch()core/vendor/illuminate/routing/Route.php on line 262
EvolutionCMS\Controllers\Actions->handleAction()core/vendor/illuminate/routing/ControllerDispatcher.php on line 48
EvolutionCMS\ManagerTheme->handle()core/src/Controllers/Actions.php on line 27
Illuminate\View\View->render()core/src/ManagerTheme.php on line 421
Illuminate\View\View->renderContents()core/vendor/illuminate/view/View.php on line 91
Illuminate\View\View->getContents()core/vendor/illuminate/view/View.php on line 122
Illuminate\View\Engines\CompilerEngine->get()core/vendor/illuminate/view/View.php on line 139
Illuminate\View\Engines\PhpEngine->evaluatePath()core/vendor/illuminate/view/Engines/CompilerEngine.php on line 61
Illuminate\View\Engines\CompilerEngine->handleViewException()core/vendor/illuminate/view/Engines/PhpEngine.php on line 60

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Is this a bug?

[q2apro]

The error happens every time in the EvoCMS -> Configuration, when hitting the Save button.

Class 'SimpleXmlElement' not found (View: /var/www/html/manager/views/page/2.blade.php)

$items = fetchCacheableRss($url, 'channel/item', function(SimpleXMLElement $entry){

Error information
File /var/www/html/core/functions/rss.php Line 14

    $xml = new SimpleXmlElement($content);

[Dmi3yy]

Its. bug with php, need add php module Xml

[q2apro]

Via SSH in the server:

sudo apt-get install php-xml
sudo service apache2 restart

Thanks a lot @Dmi3yy