Mrthdrb

In my success.phtml , $block->getViewOrderUrl() gives a order url with order id(entity id) .

dev/tests/functional/tests/app/Magento/Checkout/Test/Block/Onepage/Success.php

/sales/order/view/order_id/173569/

How to get this order id alone - 173569 in success.phtml.

I don't see any functions in success.php

You can try this one to get the order Id alone:

$block->getOrderId()

UPDATE:

You can override the Block file of checkout success one page using preference and define your own method to get the order Id.

Try this:

In your custom module's di.xml file add this:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
 <preference for="MagentoCheckoutBlockOnepageSuccess" type="VendorModuleBlockOnepageSuccess" />
</config> 

Now create Success.php Block file in Folder VendorModuleBlockOnepage

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace VendorModuleBlockOnepage;

use MagentoCustomerModelContext;
use MagentoSalesModelOrder;

/**
 * One page checkout success page
 *
 * @api
 * @since 100.0.2
 */
class Success extends MagentoFrameworkViewElementTemplate

 /**
 * @var MagentoCheckoutModelSession
 */
 protected $_checkoutSession;

 /**
 * @var MagentoSalesModelOrderConfig
 */
 protected $_orderConfig;

 /**
 * @var MagentoFrameworkAppHttpContext
 */
 protected $httpContext;

 /**
 * @param MagentoFrameworkViewElementTemplateContext $context
 * @param MagentoCheckoutModelSession $checkoutSession
 * @param MagentoSalesModelOrderConfig $orderConfig
 * @param MagentoFrameworkAppHttpContext $httpContext
 * @param array $data
 */
 public function __construct(
 MagentoFrameworkViewElementTemplateContext $context,
 MagentoCheckoutModelSession $checkoutSession,
 MagentoSalesModelOrderConfig $orderConfig,
 MagentoFrameworkAppHttpContext $httpContext,
 array $data = []
 ) 
 parent::__construct($context, $data);
 $this->_checkoutSession = $checkoutSession;
 $this->_orderConfig = $orderConfig;
 $this->_isScopePrivate = true;
 $this->httpContext = $httpContext;
 

 /**
 * Render additional order information lines and return result html
 *
 * @return string
 */
 public function getAdditionalInfoHtml()
 
 return $this->_layout->renderElement('order.success.additional.info');
 

 /**
 * Initialize data and prepare it for output
 *
 * @return string
 */
 protected function _beforeToHtml()
 
 $this->prepareBlockData();
 return parent::_beforeToHtml();
 

 /**
 * Prepares block data
 *
 * @return void
 */
 protected function prepareBlockData()
 
 $order = $this->_checkoutSession->getLastRealOrder();

 $this->addData(
 [
 'is_order_visible' => $this->isVisible($order),
 'view_order_url' => $this->getUrl(
 'sales/order/view/',
 ['order_id' => $order->getEntityId()]
 ),
 'print_url' => $this->getUrl(
 'sales/order/print',
 ['order_id' => $order->getEntityId()]
 ),
 'can_print_order' => $this->isVisible($order),
 'can_view_order' => $this->canViewOrder($order),
 'order_id' => $order->getIncrementId()
 ]
 );
 

 /**
 * Is order visible
 *
 * @param Order $order
 * @return bool
 */
 protected function isVisible(Order $order)
 
 return !in_array(
 $order->getStatus(),
 $this->_orderConfig->getInvisibleOnFrontStatuses()
 );
 

 /**
 * Can view order
 *
 * @param Order $order
 * @return bool
 */
 protected function canViewOrder(Order $order)
 
 return $this->httpContext->getValue(Context::CONTEXT_AUTH)
 && $this->isVisible($order);
 

 /**
 * @return string
 * @since 100.2.0
 */
 public function getContinueUrl()
 
 return $this->_storeManager->getStore()->getBaseUrl();
 


 /**
 * @return string
 * getOrigId
 */
 public function getOrigId()
 
 return $this->_checkoutSession->getLastRealOrder()->getEntityId();
 

Then you can now get the Order Id(Entity Id) in your .phtml template like this:

$block->getOrigId()